Transcript
ACRP
AIRPORT
COOPERATIVE
RESEARCH
PROGRAM
SYNTHESIS 22
Common Airport Pavement
Maintenance Practices
A Synthesis of Airport Practice
Sponsored by
the Federal
Aviation Administration
ACRP OVERSIGHT COMMITTEE*
TRANSPORTATION RESEARCH BOARD 2011 EXECUTIVE COMMITTEE*
CHAIR
OFFICERS
Chair: Neil J. Pedersen, Administrator, Maryland State Highway Administration, Baltimore
Vice Chair: Sandra Rosenbloom, Professor of Planning, University of Arizona, Tucson
Executive Director: Robert E. Skinner, Jr., Transportation Research Board
JAMES WILDING
Metropolitan Washington Airports
Authority (retired)
VICE CHAIR
JEFF HAMIEL
Minneapolis–St. Paul
Metropolitan Airports Commission
MEMBERS
JAMES CRITES
Dallas–Ft. Worth International Airport
RICHARD DE NEUFVILLE
Massachusetts Institute of Technology
KEVIN C. DOLLIOLE
Unison Consulting
JOHN K. DUVAL
Austin Commercial, LP
KITTY FREIDHEIM
Freidheim Consulting
STEVE GROSSMAN
Jacksonville Aviation Authority
TOM JENSEN
National Safe Skies Alliance
CATHERINE M. LANG
Federal Aviation Administration
GINA MARIE LINDSEY
Los Angeles World Airports
CAROLYN MOTZ
Hagerstown Regional Airport
RICHARD TUCKER
Huntsville International Airport
EX OFFICIO MEMBERS
PAULA P. HOCHSTETLER
Airport Consultants Council
SABRINA JOHNSON
U.S. Environmental Protection Agency
RICHARD MARCHI
Airports Council International—
North America
LAURA McKEE
Air Transport Association of America
HENRY OGRODZINSKI
National Association of State Aviation
Officials
MELISSA SABATINE
American Association of Airport
Executives
ROBERT E. SKINNER, JR.
Transportation Research Board
SECRETARY
CHRISTOPHER W. JENKS
Transportation Research Board
*Membership as of October 2010.
MEMBERS
J. BARRY BARKER, Executive Director, Transit Authority of River City, Louisville, KY
DEBORAH H. BUTLER, Executive Vice President, Planning, and CIO, Norfolk Southern
Corporation, Norfolk, VA
WILLIAM A.V. CLARK, Professor, Department of Geography, University of California,
Los Angeles
EUGENE A. CONTI, JR., Secretary of Transportation, North Carolina DOT, Raleigh
JAMES M. CRITES, Executive Vice President of Operations, Dallas-Fort Worth International
Airport, TX
PAULA J. HAMMOND, Secretary, Washington State DOT, Olympia
ADIB K. KANAFANI, Cahill Professor of Civil Engineering, University of California, Berkeley
SUSAN MARTINOVICH, Director, Nevada DOT, Carson City
MICHAEL R. MORRIS, Director of Transportation, North Central Texas Council of Governments,
Arlington
TRACY L. ROSSER, Vice President, Regional General Manager, Wal-Mart Stores, Inc.,
Mandeville, LA
STEVEN T. SCALZO, Chief Operating Officer, Marine Resources Group, Seattle, WA
HENRY G. (GERRY) SCHWARTZ, JR., Chairman (retired), Jacobs/Sverdrup Civil, Inc., St. Louis, MO
BEVERLY A. SCOTT, General Manager and CEO, Metropolitan Atlanta Rapid Transit Authority,
Atlanta, GA
DAVID SELTZER, Principal, Mercator Advisors LLC, Philadelphia, PA
LAWRENCE A. SELZER, President and CEO, The Conservation Fund, Arlington, VA
KUMARES C. SINHA, Olson Distinguished Professor of Civil Engineering, Purdue University,
West Lafayette, IN
DANIEL SPERLING, Professor of Civil Engineering and Environmental Science and Policy;
Director, Institute of Transportation Studies; and Interim Director, Energy Efficiency Center,
University of California, Davis
KIRK T. STEUDLE, Director, Michigan DOT, Lansing
DOUGLAS W. STOTLAR, President and CEO, Con-Way, Inc., Ann Arbor, MI
C. MICHAEL WALTON, Ernest H. Cockrell Centennial Chair in Engineering, University of
Texas, Austin
EX OFFICIO MEMBERS
PETER H. APPEL, Administrator, Research and Innovative Technology Administration, U.S.DOT
J. RANDOLPH BABBITT, Administrator, Federal Aviation Administration, U.S.DOT
REBECCA M. BREWSTER, President and COO, American Transportation Research Institute,
Smyrna, GA
ANNE S. FERRO, Administrator, Federal Motor Carrier Safety Administration, U.S.DOT
JOHN T. GRAY, Senior Vice President, Policy and Economics, Association of American Railroads,
Washington, DC
JOHN C. HORSLEY, Executive Director, American Association of State Highway and
Transportation Officials, Washington, DC
DAVID T. MATSUDA, Deputy Administrator, Maritime Administration, U.S.DOT
VICTOR M. MENDEZ, Administrator, Federal Highway Administration, U.S.DOT
WILLIAM W. MILLAR, President, American Public Transportation Association, Washington, DC
TARA O’TOOLE, Under Secretary for Science and Technology, U.S. Department of Homeland
Security, Washington, DC
ROBERT J. PAPP (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, U.S. Department of
Homeland Security, Washington, DC
CYNTHIA L. QUARTERMAN, Administrator, Pipeline and Hazardous Materials Safety
Administration, U.S.DOT
PETER M. ROGOFF, Administrator, Federal Transit Administration, U.S.DOT
DAVID L. STRICKLAND, Administrator, National Highway Traffic Safety Administration, U.S.DOT
JOSEPH C. SZABO, Administrator, Federal Railroad Administration, U.S.DOT
POLLY TROTTENBERG, Assistant Secretary for Transportation Policy, U.S.DOT
ROBERT L. VAN ANTWERP (Lt. Gen., U.S. Army), Chief of Engineers and Commanding
General, U.S. Army Corps of Engineers, Washington, DC
BARRY R. WALLERSTEIN, Executive Officer, South Coast Air Quality Management District,
Diamond Bar, CA
*Membership as of March 2011.
AIRPORT COOPERATIVE RESEARCH PROGRAM
ACRP SYNTHESIS 22
Common Airport Pavement
Maintenance Practices
A Synthesis of Airport Practice
CONSULTANTS
JERRY HAJEK
Applied Research Associates/ERES Division
Toronto, ON, Canada
JIM W. HALL
Applied Research Associates, Inc.
Vicksburg, Mississippi
and
DAVID K. HEIN
Applied Research Associates, Inc.
Champaign, Illinois
S UBSCRIBER C ATEGORIES
Aviation • Maintenance and Preservation • Pavements
Research Sponsored by the Federal Aviation Administration
TRANSPORTATION RESEARCH BOARD
WASHINGTON, D.C.
2011
www.TRB.org
AIRPORT COOPERATIVE RESEARCH PROGRAM
ACRP SYNTHESIS 22
Airports are vital national resources. They serve a key role in
transportation of people and goods and in regional, national, and
international commerce. They are where the nation’s aviation system connects with other modes of transportation and where federal
responsibility for managing and regulating air traffic operations
intersects with the role of state and local governments that own and
operate most airports. Research is necessary to solve common operating problems, to adapt appropriate new technologies from other
industries, and to introduce innovations into the airport industry.
The Airport Cooperative Research Program (ACRP) serves as one
of the principal means by which the airport industry can develop
innovative near-term solutions to meet demands placed on it.
The need for ACRP was identified in TRB Special Report 272:
Airport Research Needs: Cooperative Solutions in 2003, based on
a study sponsored by the Federal Aviation Administration (FAA).
The ACRP carries out applied research on problems that are shared
by airport operating agencies and are not being adequately
addressed by existing federal research programs. It is modeled after
the successful National Cooperative Highway Research Program
and Transit Cooperative Research Program. The ACRP undertakes
research and other technical activities in a variety of airport subject
areas, including design, construction, maintenance, operations,
safety, security, policy, planning, human resources, and administration. The ACRP provides a forum where airport operators can cooperatively address common operational problems.
The ACRP was authorized in December 2003 as part of the
Vision 100-Century of Aviation Reauthorization Act. The primary
participants in the ACRP are (1) an independent governing board,
the ACRP Oversight Committee (AOC), appointed by the Secretary
of the U.S. Department of Transportation with representation from
airport operating agencies, other stakeholders, and relevant industry organizations such as the Airports Council International-North
America (ACI-NA), the American Association of Airport Executives (AAAE), the National Association of State Aviation Officials
(NASAO), and the Air Transport Association (ATA) as vital links
to the airport community; (2) the TRB as program manager and secretariat for the governing board; and (3) the FAA as program sponsor. In October 2005, the FAA executed a contract with the National
Academies formally initiating the program.
The ACRP benefits from the cooperation and participation of airport professionals, air carriers, shippers, state and local government
officials, equipment and service suppliers, other airport users, and
research organizations. Each of these participants has different
interests and responsibilities, and each is an integral part of this
cooperative research effort.
Research problem statements for the ACRP are solicited periodically but may be submitted to the TRB by anyone at any time. It is
the responsibility of the AOC to formulate the research program by
identifying the highest priority projects and defining funding levels
and expected products.
Once selected, each ACRP project is assigned to an expert panel,
appointed by the TRB. Panels include experienced practitioners and
research specialists; heavy emphasis is placed on including airport
professionals, the intended users of the research products. The panels
prepare project statements (requests for proposals), select contractors,
and provide technical guidance and counsel throughout the life of the
project. The process for developing research problem statements and
selecting research agencies has been used by TRB in managing cooperative research programs since 1962. As in other TRB activities,
ACRP project panels serve voluntarily without compensation.
Primary emphasis is placed on disseminating ACRP results to the
intended end-users of the research: airport operating agencies, service
providers, and suppliers. The ACRP produces a series of research
reports for use by airport operators, local agencies, the FAA, and other
interested parties, and industry associations may arrange for workshops, training aids, field visits, and other activities to ensure that
results are implemented by airport-industry practitioners.
Project 11-03, Topic S09-02
ISSN 1935-9187
ISBN 978-0-309-14334-9
Library of Congress Control Number 2011923982
© 2011 National Academy of Sciences. All rights reserved.
COPYRIGHT INFORMATION
Authors herein are responsible for the authenticity of their materials and for
obtaining written permissions from publishers or persons who own the
copyright to any previously published or copyrighted material used herein.
Cooperative Research Programs (CRP) grants permission to reproduce
material in this publication for classroom and not-for-profit purposes.
Permission is given with the understanding that none of the material will
be used to imply TRB or FAA endorsement of a particular product, method,
or practice. It is expected that those reproducing the material in this
document for educational and not-for-profit uses will give appropriate
acknowledgment of the source of any reprinted or reproduced material. For
other uses of the material, request permission from CRP.
NOTICE
The project that is the subject of this report was a part of the Airport
Cooperative Research Program, conducted by the Transportation Research
Board with the approval of the Governing Board of the National Research
Council.
The members of the technical panel selected to monitor this project and
to review this report were chosen for their special competencies and with
regard for appropriate balance. The report was reviewed by the technical
panel and accepted for publication according to procedures established and
overseen by the Transportation Research Board and approved by the
Governing Board of the National Research Council.
The opinions and conclusions expressed or implied in this report are those
of the researchers who performed the research and are not necessarily those
of the Transportation Research Board, the National Research Council, or the
program sponsors.
The Transportation Research Board of the National Academies, the National
Research Council, and the sponsors of the Airport Cooperative Research
Program do not endorse products or manufacturers. Trade or manufacturers’
names appear herein solely because they are considered essential to the
object of the report.
Published reports of the
AIRPORT COOPERATIVE RESEARCH PROGRAM
are available from:
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Business Office
500 Fifth Street, NW
Washington, DC 20001
and can be ordered through the Internet at
http://www.national-academies.org/trb/bookstore
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and to their use for the general welfare. On the authority of the charter granted to it by the Congress in
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mission of the Transportation Research Board is to provide leadership in transportation innovation and
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www.national-academies.org
ACRP COMMITTEE FOR PROJECT 11-03
CHAIR
JULIE KENFIELD
Jacobs Engineering Group, Inc.
MEMBERS
RANDALL P. BURDETTE
Virginia Department of Aviation
KEVIN C. DOLLIOLE
Union Consulting, Inc.
LINDA HOWARD
Bastrop, Texas
ARLYN PURCELL
Port Authority of New York and New Jersey
BURR STEWART
Seattle, Washington
FAA LIAISON
PAUL DEVOTI
ACI–NORTH AMERICA LIAISON
A.J. MULDOON
AIRCRAFT OWNERS AND PILOTS ASSOCIATION
JOHN L. COLLINS
TRB LIAISON
CHRISTINE GERENCHER
Cover figure: Construction of microsurfacing layer on runway.
Credit: The Miller Group.
COOPERATIVE RESEARCH PROGRAMS STAFF
CHRISTOPHER W. JENKS, Director, Cooperative Research Programs
CRAWFORD F. JENCKS, Deputy Director, Cooperative Research
Programs
MICHAEL R. SALAMONE, Senior Program Officer
EILEEN P. DELANEY, Director of Publications
ACRP SYNTHESIS STAFF
STEPHEN R. GODWIN, Director for Studies and Special Programs
JON M. WILLIAMS, Program Director, IDEA and Synthesis Studies
GAIL R. STABA, Senior Program Officer
DON TIPPMAN, Senior Editor
CHERYL KEITH, Senior Program Assistant
DEBBIE IRVIN, Program Associate
TOPIC PANEL
GARY FUSELIER, Metropolitan Washington Airport Authority
ERIC JOHNSON, Washington State Department of Transportation
MARK C. JUSTICE, Ohio Department of Transportation
FRANK N. LISLE, Transportation Research Board
XIANMING SHI, Montana State University
QUINTON WATKINS, Prime Engineering, Inc., Atlanta
RAYMOND ZEE, Federal Aviation Administration
PAUL L. FRIEDMAN, Federal Aviation Administration (Liaison)
JEFF RAPOL, Federal Aviation Administration (Liaison)
FOREWORD
Airport administrators, engineers, and researchers often face problems for which information already exists, either in documented form or as undocumented experience and practice. This information may be fragmented, scattered, and unevaluated. As a consequence,
full knowledge of what has been learned about a problem may not be brought to bear on its
solution. Costly research findings may go unused, valuable experience may be overlooked,
and due consideration may not be given to recommended practices for solving or alleviating the problem.
There is information on nearly every subject of concern to the airport industry. Much of
it derives from research or from the work of practitioners faced with problems in their dayto-day work. To provide a systematic means for assembling and evaluating such useful information and to make it available to the entire airport community, the Airport Cooperative
Research Program authorized the Transportation Research Board to undertake a continuing project. This project, ACRP Project 11-03, “Synthesis of Information Related to Airport Practices,” searches out and synthesizes useful knowledge from all available sources
and prepares concise, documented reports on specific topics. Reports from this endeavor
constitute an ACRP report series, Synthesis of Airport Practice.
This synthesis series reports on current knowledge and practice, in a compact format,
without the detailed directions usually found in handbooks or design manuals. Each report
in the series provides a compendium of the best knowledge available on those measures
found to be the most successful in resolving specific problems.
PREFACE
This synthesis study is intended to inform airport pavement engineers and airport maintenance managers and personnel about how airports implement a pavement maintenance
management program, including inspection and tracking pavement condition, scheduling
maintenance, identifying necessary funds, and treating distresses in asphalt and concrete
pavements.
Information used in this study was acquired through a review of the literature and interviews with airport operators and industry experts.
Jerry Hajek, Jim W. Hall, and David K. Hein, Applied Research Associates, Inc., collected and synthesized the information and wrote the report. The members of the topic panel
are acknowledged on the preceding page. This synthesis is an immediately useful document
that records the practices that were acceptable within the limitations of the knowledge available at the time of its preparation. As progress in research and practice continues, new
knowledge will be added to that now at hand.
By Gail R. Staba
Senior Program Officer
Transportation
Research Board
CONTENTS
1
SUMMARY
5
CHAPTER ONE INTRODUCTION
Purpose, 5
Background, 5
Methodology, 6
Report Organization, 7
9
CHAPTER TWO DESIGN OF AIRPORT PAVEMENT
MANAGEMENT SYSTEMS
Airport Pavement Management Process, 9
Management and Technical Aspects, 9
12
CHAPTER THREE PAVEMENT INVENTORY AND EVALUATION
Pavement Inventory, 12
Pavement Evaluation Principles, 12
Evaluation of Pavement Condition, 13
Condition Analysis, 15
Pavement Evaluation for Preventive Maintenance, 16
Pavement Performance Prediction, 16
18
CHAPTER FOUR TECHNOLOGY OF PAVEMENT
PRESERVATION TREATMENTS
Survey Results, 18
Catalog of Airport Pavement Preservation Treatments, 21
22
CHAPTER FIVE IDENTIFICATION OF NEEDS
Levels of Service and Trigger Levels, 22
Identification of Needs, 23
27
CHAPTER SIX PRIORITIZATION, PLANNING, AND BUDGETING
Prioritization, 27
Programming and Budgeting, 29
Computational Support, 31
33
CHAPTER SEVEN PROJECT DESIGN AND IMPLEMENTATION
Project Design, 33
Project Implementation and Monitoring, 35
37
CHAPTER EIGHT OPERATION, SUSTAINABILITY,
AND ENHANCEMENT
Airport Pavement Management Systems Operation and Sustainability, 37
System Enhancement, 37
39
CHAPTER NINE
CONCLUSIONS
41
GLOSSARY OF TERMS
43
REFERENCES
45
APPENDIX A
SURVEY QUESTIONNAIRE AND SURVEY RESPONSES
54
APPENDIX B
CATALOG OF AIRPORT PAVEMENT PRESERVATION TREATMENTS
COMMON AIRPORT PAVEMENT
MAINTENANCE PRACTICES
SUMMARY
Every airport operator is faced with the need to maintain airside pavements in good order for
safe and efficient aircraft operation using the available budget. This synthesis describes how
airports of all sizes currently practice pavement maintenance.
Decision making for maintenance and rehabilitation (M&R) of airport pavements typically consists of two stages of sequential decisions. The first stage involves identifying
and prioritizing future pavement preservation needs, treatments, and projects, considering the needs and priorities of all airport pavements together. The objective of this stage
is to decide at a given time which pavement sections are prioritized to receive M&R treatments. The second stage consists of determining, using site-specific engineering considerations, what type(s) of M&R treatment is to be carried out on the previously selected
sections.
Although both stages are described in the synthesis, the emphasis was placed on the first
stage, identifying and prioritizing future pavement preservation needs. The main challenge
facing airport authorities is not which M&R treatment to use, but how to justify that M&R
treatments are necessary, using a judicious and objective process, and to obtain funding for
their implementation. In other words, the first priority is to select the right pavement sections
for treatment.
The synthesis describes pavement preservation practices and treatments for asphalt concrete (AC) and portland cement concrete (PCC) pavements. Pavement preservation treatments for surface-treated and aggregate-surfaced pavements are not included. The technology of pavement preservation treatments is summarized in the Catalog of Airport Pavement
Preservation Treatments in Appendix B. The Catalog contains a description of 24 common
pavement preservation treatments for AC and PCC airport pavements
The synthesis addresses both M&R treatments because these two treatment types overlap,
have a common goal, and work together to provide a cost-efficient pavement preservation
program. Special attention was paid to describing the role of preventive maintenance in pavement preservation. Preventive maintenance is carried out to prevent premature pavement
deterioration. Routine pavement maintenance that does not substantially improve the pavement surface is not included in the synthesis.
The main sources of information were an extensive literature review and a survey of airport pavement professionals representing individual airports or small groups of airports serving one small geographical area. The survey was a four-page questionnaire and is included in
Appendix A. The survey focused on the use and operation of airport pavement management
systems (APMSs), evaluation of pavement conditions, procedures used to select M&R treatments, use of preventive maintenance, identification of pavement preservation needs, funding sources, and the usage and field performance of common airport pavement preservation
treatments. Survey responses were obtained from 50 pavement maintenance professionals,
an 80% response rate for airports with daily aircraft operations ranging from a few to several
thousand flights.
2
The role of an APMS is to support the technical, engineering, and management activities of
airport personnel responsible for providing pavement infrastructure for safe and efficient operation of aircraft. The pavement management process provides systematic and objective procedures for maintaining the inventory of pavement infrastructure, monitoring pavement performance, selecting the right treatment for the right pavement at the right time, planning and
budgeting of pavement preservation activities, and evaluating the cost-effectiveness of past
pavement preservation actions. Based on the survey, more than 80% of airports have a functional APMS or are in the process of developing one. Approximately 30% of respondents rated
their APMS as excellent and essential, and about 34% rated their system as functional but in
need of improvement. The rest of the respondents were generally satisfied with their system.
The inventory of pavement infrastructure is the basic building block of an APMS. Because
pavements deteriorate with time, the inventory includes the past and the current condition of
pavements and the anticipated future pavement conditions. The predominant pavement performance modeling technique for airport pavements uses a set of characteristic pavement performance curves developed for groups (or “families”) of similar pavement sections. Pavement
condition evaluation includes the review of pavement surface distresses, roughness, friction,
presence of foreign debris, and the evaluation of pavement surface deflections. With the exceptions of a few small airports, all airports surveyed carry out periodic pavement condition
evaluation of runways using the Pavement Condition Index, with the average frequency of
3.4 years. Additional pavement evaluation cycles are utilized for timely selection and implementation of preventive maintenance treatments. The pavement evaluation results are used to
assess trends in the overall condition (the health) of the pavement network, document the funding needs and the benefits of the APMS, identify major causes of pavement deterioration, and
determine the performance of specific pavement structures and M&R treatments.
For purposes of the survey, 38 separate M&R treatments were identified; 19 for AC pavements and 19 for PCC pavements, and airport officials were asked to provide information on the
use and performance of these 38 treatments. For AC pavements, the most frequently used treatment was crack sealing using hot-poured bituminous sealant, which was used by 90% of all airport agencies that had such pavements on at least one facility. The next four most frequently used
treatments were pothole patching with hot mix, hot-mix overlay, milling and overlay, and pothole patching with cold mix. For PCC pavements, the most frequently used treatments were fulldepth slab repairs and replacement using PCC or AC materials, joint resealing using silicone
sealants, and shallow patching repairs using AC material. Based on the survey results, the average performance of the 19 M&R treatments for AC pavements was considered to be slightly better than the average performance for the 19 M&R treatments for PCC pavements.
Pavement preservation needs depend on the level of service the airport pavements are
expected to provide. For the same pavement structure, a higher level of service results in
higher M&R costs. The levels of service that can be used to guide the needs for M&R treatments include target or desirable level of service, minimum acceptable level of service, and
minimum safety-related level of service. Trigger values can be used to provide guidance on
timing for M&R treatments. The identification of needs is discussed for two time horizons:
short-term planning for the time horizon of about 5 years or less, and long-term planning for
the time horizon exceeding 5 years. Approximately 56% of respondents systematically identify pavement sections that would benefit from pavement maintenance.
Prioritization of M&R projects is typically based on priority levels that are related to the
levels of service used to identify pavement preservation needs. Prioritization can be based on
a single characteristic, such as the Pavement Condition Index, or on a composite indicator
that combines several characteristics.
Budgeting takes into account not only pavement preservation needs but also other airfield
needs affecting airport pavements, such as projects involving safety and functional improve-
3
ments, underground utilities, and in-pavement lighting. Budgetary issues involve financial
considerations related to the available funding and the time when the funding is available and
operational considerations that include the impact on airport operations and safety during
construction. Based on the survey, all airport agencies that have an APMS use a software
application to facilitate the identification of needs, prioritization, and budgeting. About 53%
of survey respondents reported using MicroPAVER, 13% used other commercial software,
and 34% used in-house software.
With a few exceptions, all airport authorities surveyed already operate or are developing an
APMS. The average age of the existing systems at the time of this survey was 9 years. The
reported challenge for most of the agencies is not to develop an APMS, but to sustain and
enhance its operation. Approximately 27% of airports that have an APMS characterized their
systems as operational, but in need of improvement. The attributes that contribute to the successful operation and sustainability of an APMS include long-term commitment and support
from decision makers, data integrity and timeliness, periodic reporting of results, meeting user
needs through ongoing improvements, and a provision for training and succession planning.
In addition to ongoing system enhancements, a structured comprehensive review and
enhancement of the APMS operations can be done using gap analysis and benchmarking.
5
CHAPTER ONE
INTRODUCTION
This report describes the results of ACRP Project 11-03,
S09-02, Common Airport Pavement Maintenance Practices.
The objective of the synthesis is to provide information for
airport managers and engineers on how airports implement
airport pavement maintenance systems (APMSs), including
inspection and tracking pavement condition, scheduling
maintenance and rehabilitation (M&R), identifying necessary funds and treating distresses in asphalt concrete (AC)
and portland cement concrete (PCC).
PURPOSE
There is a large amount of information available on pavement maintenance; however, the information is dispersed
and not always current. The specific objectives of the synthesis include:
• Documenting current pavement maintenance practices;
• Synthesizing relevant information by comparing, evaluating, and prioritizing it; and
• Identifying ongoing and recently completed research in
the area of airport pavement maintenance programs and
treatments.
Pavement maintenance as discussed in this synthesis
includes both maintenance treatments such as crack sealing
and rehabilitation treatments such as overlays. All types of
M&R treatments are needed for cost-effective preservation of
airport pavements. The synthesis describes pavement M&R
practices for AC and PCC pavements; however, such practices for surface-treated and aggregate-surfaced pavements
are not included.
BACKGROUND
Airport pavement maintenance practices generally follow the
objectives, principles, and methodology of highway pavement management and asset management. There are several
publications that provide useful information on pavement
management procedures, including pavement condition evaluation, selection of maintenance and rehabilitation treatments, priority analysis, and other pavement management
topics. For example, FAA Advisory Circular on Guidelines
and Procedures for Maintenance of Airport Pavements
(2007); FAA Advisory Circular on Airport Pavement Management Program (2006); Transportation Research Circular
E-C127: Implementation of an Airport Pavement Management System (Tighe and Covalt 2008); Unified Facilities Criteria on Pavement Maintenance Management (2008); Modern Pavement Management (Hass et al. 1994); Pavement
Management for Airports, Roads, and Parking Lots (Shahin
1994); and the AASHTO Pavement Management Guide
(2001). The FHWA Pavement Preservation Compendium II
(2006) describes many practical aspects of preventive maintenance applied to highway pavements.
The activities included for cost-effective preservation of
airport pavements can be divided into two broad stages. The
first stage includes identification and selection of future M&R
treatments and projects considering the needs of all airport
pavements. The objective of the first stage is to develop a
budget for a Capital Improvement Program (CIP) or for a similar infrastructure preservation program. The second stage
involves the design and construction of the M&R treatments
for specific pavement sections identified during the first stage.
In the context of pavement management, the first stage
activities represent the network-level management and the second stage activities the project-level management. Although
both pavement management stages are described in the synthesis, the emphasis is on the network-level activities (how to
select the right M&R treatments for the right pavements)
rather than on materials and construction methods used for
pavement preservation (how to design and build the right treatment). The reasons for emphasizing network-level activities
rather than project-level activities include:
• Activities carried out at the network level, such as a systematic and objective assessment of pavement network
condition, have universal applicability, whereas projectlevel activities often depend on airport-specific and sitespecific conditions.
• Some maintenance treatments, such as microsurfacing
and slurry seals, are constructed according to industryor region-wide specifications with little input by local
airport authorities.
• Pavement maintenance management practices on the network level are the cornerstone of pavement preservation.
The main challenge facing airport authorities is not which
pavement preservation treatment to use on a particular
section, but to justify that M&R treatments are necessary
and to obtain funding for their implementation.
• Information on airport pavement maintenance practices
on the network level needs to be documented.
6
Combining Maintenance and Rehabilitation
METHODOLOGY
This synthesis is concerned with both pavement maintenance
and rehabilitation treatments, because these treatments overlap
and are an integral part of a pavement preservation program.
Guidelines and manuals on pavement preservation typically
combine M&R treatments. For example, FAA Advisory Circular on Guidelines and Procedures for Maintenance of Airport Pavements (2007) describes M&R treatments together
using the term “maintenance and repair.” MicroPAVER
(2003), a predominant pavement management software application, recommends pavement preservation strategies using
several M&R treatments.
The synthesis is based on information obtained by an extensive
literature review, a targeted survey of airport pavement maintenance professionals, follow-up telephone interviews, and
interviews and discussions with pavement experts, including
technical staff representing airports of different sizes located in
different regions of the country.
Pavement maintenance may also include routine maintenance that does not substantially improve the pavement surface, such as removal of debris, snow and ice control, repainting of pavement markings, maintenance of in-pavement lights,
and removal of rubber deposits. These routine maintenance
activities are not included in the synthesis.
Role of Preventive Maintenance (Preservation)
Preventive maintenance is carried out to prevent premature
pavement deterioration or to slow the rate of deterioration. It is
accomplished when the treatment is most effective, typically
when the pavement is fairly new. Preventive maintenance may
include, for example, crack sealing or machine patching of
AC pavements, or resealing of PCC pavements. Preventive
maintenance is an integral part of a pavement preservation
program—of applying the right treatment to the right pavement at the right time.
Preventive maintenance has a special standing in the area
of pavement preservation for several reasons:
• Preventive maintenance embodies the age-old experience that a stitch in time saves nine.
• The term preventive maintenance, and the concept of
preventive maintenance, have become widely accepted
and are well-liked by many practitioners.
• The successful application of preventive maintenance
programs depends on the timeliness of the application
that includes:
– Detailed pavement surveys that can pinpoint when
the treatment produces best results. For example,
routing and sealing of longitudinal and transverse
cracks in AC pavements produces favorable results
after the cracks are well-defined, but before single
cracks develop into multiple cracks.
– Dedicated funding so that the treatment can be carried out at the right time without funding delays.
Consequently, the emphasis on preventive maintenance highlights the need for timely pavement preservation actions and
contributes to judicious monitoring of pavement condition
and to the establishment of dedicated maintenance budgets.
Literature Review
Airport pavement maintenance technology is documented
in many publications such as books, guidelines, manuals of
practice, specifications, circulars, and field performance and
research reports. The primary information sources included
the following:
• U.S.DOT—The FAA has issued several applicable
advisory circulars referenced previously. The FHWA
and its Office of Asset Management has produced several useful publications, notably the Pavement Preservation Toolbox (2006).
• U.S. Department of Defense (DOD). The Air Force
has issued eight applicable Engineering Technical
Letters that provide practical guidance for M&R of
airfield pavements; for example, Maintenance and
Repair of Rigid Airfield Pavement Surfaces, Joints,
and Cracks (2004). The DOD also issues Unified
Facilities Criteria (UFC) publications. The UFC series
contains more than a dozen relevant reports and technical manuals; for example, Pavement Maintenance
Management (2004).
• Reports produced by the Strategic Highway Research
Program (SHRP), such as Asphalt Pavement Repair
Manuals of Practice (1993) and Concrete Pavement
Repair Manuals of Practice (1993), and reports produced by SHRP Long Term Pavement Performance
Program, such as Comparison of Rehabilitation Strategies for AC Pavements (2000).
• National and international industry associations such as
International Slurry Surfacing Association, National
Asphalt Paving Association, American Concrete Pavement Association, and The Asphalt Institute.
• Technical associations and foundations such as TRB,
American Society of Civil Engineers, Association of
Asphalt Paving Technologists, Foundation for Pavement
Preservation, National Centre for Pavement Preservation, Airfield Asphalt Technical Program, and Innovative
Pavement Research Foundation.
• State sources. Several state transportation agencies
developed comprehensive pavement maintenance guides,
notably California (2008), Michigan (1999), Minnesota
(2001), and Ohio (2001).
This synthesis contains only a small selection from the available information, with the objective to provide an overview
7
of common airport pavement maintenance practices and their
current application.
Many information sources, such as pavement management
guides, specifications, manuals, and field performance reports,
used for the preparation of the synthesis, were written for roadway pavements. There are differences between airfield and roadway pavements. Airfield pavements are subjected to a greater
range of wheel loads, and wheel load applications are relatively
infrequent and more spatially distributed (less channelized) as
compared with roadway pavements. However, both airfield and
roadway pavements are built and maintained using the same construction technology (materials, construction equipment, and
construction methods), are supported by similar subgrade soils,
and are exposed to a similar environment.
There are also differences between pavement management
procedures used for airport pavement networks and roadway
pavement networks. These differences are caused primarily
by the differences in the size of airport and roadway networks.
The large size of roadway networks, particularly networks
managed by state transportation agencies, leads to the development of customized pavement management software and
pavement management procedures. For example, the customized software may incorporate an interface with other corporate databases and management systems, and include a
customized approach to generating project priorities. Large
roadway networks are also built on a variety of subgrades and
in different environmental zones, necessitating more sophisticated prediction of pavement performance and the selection
of M&R treatments. Nevertheless, the management of both
airport and roadway networks is based on the same management principles, and uses similar management procedures and
frequently the same pavement management software.
There is also a degree of similarity in the mechanism for
funding of pavement preservation for roadway pavements and
for airport pavements by external agencies, and in the consequent requirement to justify funding requests. Airfield pavement preservation is primarily funded by the FAA with some
contribution by the states; roadway pavement preservation, for
Interstate and primary highways, receives funding from the
FHWA. Both federal funding agencies require recipients to
report periodically on the condition and utilization of pavement networks receiving funding. However, unlike airfield
pavements, many roadway pavements are primarily funded by
their owner: the state, county, or a municipality.
Survey of Pavement Maintenance Professionals
The first systematic assessment of airport pavement management practices in the United States was carried out by Broten
and Wade (2004) in 2003, and included a survey of all 50 state
aviation agencies. The survey focused on how the state aviation agencies were using their APMSs. The survey documented widespread use of APMSs and the positive impact the
APMS had on the overall condition of airport pavements.
Unlike the previous survey, the synthesis survey did not target state aviation agencies, but individual pavement maintenance professionals representing individual airports or small
groups of airports serving one small geographical area.
The survey of airport pavement maintenance practitioners
representing individual airports was the main tool for gathering information on current maintenance practices. The survey
questionnaire is included in Appendix A. Key survey results
are presented in subsequent chapters of this synthesis, with
additional results presented in Appendix B.
The survey and subsequent interviews focused on the following topics:
• Use of an APMS and experience with its operation. The
topics included the age of the APMS, type of software
used, and the involvement of consultants in the operation of the APMS.
• Evaluation of pavement condition, including periodic
evaluation of pavement surface distresses, roughness,
friction, and pavement surface deflections.
• Procedures used to select best pavement rehabilitation
treatments.
• Use of preventive maintenance, including the existence
of a dedicated budget for preventive maintenance.
• Sources of funding and procedures used to obtain funding for pavement preservation activities.
• Use and performance of common pavement M&R treatments, including new and innovative pavement preservation treatments.
The survey questionnaire was sent to 62 airports in 34 states
to obtain information on current practices in airport pavement
maintenance and the application of pavement management
systems (PMSs) to track pavement performance and aid in
planning and budgeting. Survey respondents were selected to
represent different geographic and climatic regions, airports of
different sizes, and airports with different pavement types. Figure 1 shows the locations of the airports that responded to the
survey.
In total, 50 completed surveys were received, representing
approximately an 80% response rate. Figure 2 shows the average daily aircraft operations for the airports included in the
survey, and indicates that the responses were representative of
airports of all sizes. The average number of daily aircraft
operations ranged from one to about three thousand and was
obtained from AirNav.com.
REPORT ORGANIZATION
The next seven chapters are arranged in the technological
order of developing, operating, and sustaining an APMS, as
shown in Figure 3. The names of the seven technological
8
FIGURE 1 Locations of airports that responded to the survey.
steps given in Figure 3 are also the titles of the next seven
chapters (chapters two through eight). Chapter nine contains
conclusions and suggestions for further research. The report
also includes References and a Glossary of Terms.
Appendix A presents the survey questionnaire and the
survey results that are not included in the body of the report,
and Appendix B presents a Catalog of Airport Pavement
Preservation Treatments.
1. Design of APMS
Needs of the users
Expected results
2. Pavement inventory & evaluation
Inventory and database
Pavement evaluation
Performance prediction
Network Level:
Selecting
the right
3. Technology of pavement
preservation treatments
section at the right
time
Number of average daily
aircraft operations
4. Identification of needs
Levels of service
Preventive
maintenance
4000
Other pavement
preservation needs
3000
2000
5. Prioritization, planning and budgeting
1000
0
0
20
40
Sequential airport number
60
FIGURE 2 Number of average daily aircraft
operations for airports included in the
survey.
6. Project design and
implementation
7. Operation, sustainability
and enhancement
FIGURE 3 Main components of an APMS.
Project Level:
Designing and
implementing
the right treatment
9
CHAPTER TWO
DESIGN OF AIRPORT PAVEMENT MANAGEMENT SYSTEMS
This chapter describes the main features of an APMS and its
use by airport agencies. It also describes the potential benefits of the APMS, and basic steps necessary for the successful design of an APMS. More than 80% of airports that
responded to the survey reported that they have a functional
APMS or are in the process of developing one. The primary
technical resource for this chapter is the FAA AC 150/53807A, Advisory Circular on Airport Pavement Management
Program.
AIRPORT PAVEMENT MANAGEMENT PROCESS
An APMS includes all activities connected with pavement
infrastructure, including the initial pavement design and
construction, and the subsequent pavement maintenance and
rehabilitation activities. The APMS is part of airport asset
management that includes the management of all core airport
assets including pavements, buildings, and guidance systems.
The role of an APMS is to support technical, engineering,
and management activities of airport personnel responsible
for providing pavement infrastructure for safe and efficient
operation of aircraft. The pavement management process
provides systematic and objective procedures for maintaining the inventory of pavement infrastructure, monitoring
pavement performance, planning and budgeting of pavement
preservation activities, and evaluating the cost-effectiveness
of past pavement preservation actions. The main components
of an APMS, grouped into seven main activities, are shown
in Figure 3 in chapter one.
Current Use of Airport Pavement
Management Systems
The 2003 survey of state aviation agencies indicated that 84%
of the state agencies used a PMS, and that agencies using an
APMS reported improvements in pavement condition over
time (Broten and Wade 2004). The widespread use of APMSs
by state aviation agencies was attributed partially, in the
Transportation Research Circular E-C127: Implementation
of an Airport Pavement Management System (Tighe and Covalt 2008), to the passage of Public Law 103-305 in 1994. This
law requires a public airport to implement an effective airport
pavement maintenance management system to be eligible for
federal funding for pavement preservation.
Synthesis survey results indicated that 60% of all airports
operate an APMS, 23% of airports are developing an APMS,
and that about 17% of airports do not have an APMS. Several
airports that are developing or do not have an APMS reported
that they already carry out periodic pavement condition surveys
or that periodic pavement condition surveys are carried out
by their state aviation agency. Pavement condition surveys are
an important component of an APMS.
Of those airports that responded to the survey, the average
age of the APMS being used is approximately 9 years. For
comparison, Broten and Wade (2004) reported that the average age of the APMS used by state aviation agencies was
10.7 years. The distribution of the age of APMSs is shown in
Figure 4. Considering the usage of the APMS and their age,
airport pavement management technology can be considered
to be mature.
Approximately 30% of the airport authorities who already
have a functional APMS characterized their system as excellent and essential, and about 27% characterized their APMS
as functional, but in need of improvement (Figure 5). Approximately 34% of the agencies characterized their APMS as
accepted and used. None of the agencies reported that their
APMS is not useful.
MANAGEMENT AND TECHNICAL ASPECTS
An APMS design includes the establishment of its management and technical aspects. Management aspects include decisions regarding the overall system operation (e.g., in-house or
using outside staff or consultants), securing the budget for
the operation of the system, appointing staff, and establishing reporting relationships between the APMS staff and other
airport agency staff. The successful operation of an APMS
requires that it be well-integrated into the decision-making
process of the agency and that it be supported by the airport
management.
Technical aspects are concerned with the establishment of
a database for the storage and retrieval of pavement-related
data, selecting APMS software, choosing the methodology
for pavement condition evaluation, establishing procedures
for estimating pavement deterioration, and selecting the most
cost-effective M&R treatments.
10
40
20
0
<2 years
3–5 years 5–10 years 10+ years
Age of Pavement Management System
FIGURE 4 Age distribution of airport pavement
management systems.
Pavement Management on the Network
and Project Levels
Brief definitions of the network and project pavement management are provided in the Glossary of Terms. The division
of APMS activities between the network and project levels is
also shown in Figure 2 (see chapter one). For smaller airports,
consisting of only one or two runways and a few taxiways and
aprons, the network-level pavement management may include
only a handful of pavement sections, whereas large airports
may have hundreds of sections. Consequently, network-level
management needs and procedures depend on airport size.
Pavement preservation at large airports typically uses specialized pavement management software.
Project-level management activities, which concern the
design and construction of M&R treatments for a specific pavement section, tend to be similar for all airports. The main difference is in the scale and importance of specific M&R projects.
For large M&R projects, or for projects with high demand
on the reliability of pavement design, advanced engineering
design and quality control procedures are typically used to
minimize costs and achieve product quality and reliability.
Benefits and Costs of an Airport Pavement
Management System
40
30
20
Figure 6 shows how airports use different features of an
APMS. For example, approximately 90% of airports use
their APMS system to track the pavement condition and prepare budgets. Only about 45% of respondents use the system
to determine the performance of past M&R treatments.
100
75
50
25
Excellent and
Benefits
System is Functional but
essential outweigh costs accepted and
needs
improvement
used
FIGURE 5 Experience with airport pavement management
systems.
Obtain
funding
Prepare
budgets
Evaluate past
treatments
0
Predict
future
performance
0
10
Track
pavement
condition
Percent of respondents
APMS literature confirms that considerable benefits can be
obtained by agencies through the following capabilities of
the APMS:
• Computerized database—An APMS promotes the
development of a computerized database that facilitates
the organization and storage of all pavement-related
data (such as pavement structural and condition data) in
one place and with easy retrieval.
• Objective monitoring of pavement condition—The
operation of an APMS requires periodic, systematic,
and objective monitoring of pavement conditions. This
leads to the objective identification of pavement preservation needs and enables funding agencies to allocate
M&R funds to different airports based on reliable data.
• Establishment of pavement deterioration rates—The
deterioration rates are used to estimate when maintenance
and rehabilitation treatment will be needed. They can be
also used to determine the service lives of specific M&R
treatments and to identify pavement sections and pavement treatments that are deteriorating at abnormally high
rates. The life spans, together with costs, are used to calculate cost-effectiveness of pavement M&R treatments.
• Planning and budgeting—An APMS allows the user
to logically select, or even optimize, the list of pavement
M&R treatments for a given budget.
• Obtaining funding—An APMS facilitates the systematic identification and documentation of pavement preservation needs. The APMS is a prerequisite for obtaining
federal and/or state funding for M&R of airport pavements, and aids in the justification of M&R funding
from upper management.
• Flexibility of operation—An APMS fosters the need
for thorough documentation of the pavement management process. The existence of a documented pavement
management process enables agencies to adjust to
changes, particularly to changes concerning agency personnel and consultants operating the system or providing system support.
Percent of respondents
Percent of respondents
60
Usage of APMS features
FIGURE 6 Use of the features and results provided by
airport pavement management systems.
11
The costs associated with APMS include the initial costs
to develop the system, establish a pavement management
database, and train the personnel. Subsequent ongoing costs of
operating the system include periodic pavement condition
surveys, system maintenance, and modifications and improvements to the system.
Initial Design of Airport Pavement
Management Systems
The initial design of an APMS is important for ensuring the
future use and sustainability of the APMS operation. A comprehensive summary of design activities for successful implementation and operation of an APMS is provided in Transportation Research Circular E-C127 (Tighe and Covalt 2008).
Briefly, the design and implementation of an APMS includes
the following activities:
• Obtain a commitment to establish and operate an
APMS and appropriate funding to do so from airport
management.
• Identify potential users of the system and determine
their needs.
• Decide who will develop and operate the system (internal staff, consultant, or a combination of the two).
• Select APMS software.
• Develop a database including sectioning of the network
and initial pavement condition evaluation.
• Customize software to reflect local input values such as
pavement deterioration rates, M&R policies, typical unit
costs of M&R treatments, and agency-specific preferences and priorities concerning the selection of M&R
treatments.
• Customize software to incorporate agency preferences
regarding data analysis and reporting, such as network
condition analysis and the incorporation of geographic
information systems (GIS).
• Provide initial and ongoing staff training.
• Construct a follow-up plan to ensure that data are updated
(e.g., periodic pavement condition evaluation and updating
the database to record new M&R activities) and that the
software keeps pace with new developments.
12
CHAPTER THREE
PAVEMENT INVENTORY AND EVALUATION
The inventory of pavement infrastructure is the basic building block of an APMS. Because pavements deteriorate with
time, the inventory includes past and current condition of
pavements and anticipates future condition. This chapter provides a brief description of the main features of pavement
inventory and procedures used for the assessment of pavement
condition. Evaluation procedures are described for pavement surface distresses, roughness, friction, and pavement
deflection testing. With the exception of a few small airports,
all airports surveyed carry out periodic pavement condition
surveys of runways using the Pavement Condition Index
(PCI), with an average survey frequency of 3.4 years.
PAVEMENT INVENTORY
The documentation of pavement inventory is a prerequisite
for a systematic pavement condition evaluation and the selection of M&R treatments on the network level. On the project
level, pavement inventory data are essential for the design of
M&R treatments. The inventory includes the size and main
characteristics of pavement assets and their condition. Preferably, pavement inventory is viewed and organized as part of
an airport asset inventory. The U.S.DOT developed the Data
Integration Primer (2001), which explains principles and
options for developing integrated asset management databases.
There is also the ASTM Standard E177-96, Standard Guide
for Prioritization of Data Needs for Pavement Management
(ASTM 2002).
A pavement inventory divides the airport pavement network into homogeneous pavement sections with the same
pavement structure and a similar pavement condition throughout. A pavement section is the basic building block for pavement inventory. It is also a basic unit for pavement preservation decision making. An M&R project can be carried out on
a single pavement section. In other words, a section is established as a “repair unit”—a portion of the network that can be
managed and repaired independently from other sections
(Tighe and Covalt 2008).
The pavement network is typically divided into four levels according to specifications given in ASTM Standard D
5340 (2003) or in FAA Advisory Circular on Guidelines and
Procedures for Maintenance of Airport Pavements (2007):
1. Network—represents the entire pavement infrastructure managed by the airport authority.
2. Branch—a part of the network that serves a specific
purpose. Typical branches are runways, taxiways, aprons
or ramps, and airside pavements; for example, each
airport runway is considered to be a branch.
3. Section—a part of a branch that has a uniform pavement structure (and construction and maintenance
history), traffic loads, and pavement condition. It is the
basic repair unit.
4. Sample units—a part of a section created to carry
out pavement condition surveys based on the ASTM
standard. The maximum size of the sampling unit for
AC and PCC pavements is specified in the standard.
Data storage and retrieval is facilitated by APMS software
such as MicroPAVER (2003). As a minimum, the pavement
inventory data for each section includes the following:
• Section identification—functional class (branch) and
dimensions of the pavement section.
• Location of the section—for example, within the branch,
keel, or outer wings.
• Pavement structure—date of the original construction
and the description of pavement structure. The description includes thickness and basic material properties of
all layers, both the original layers and the subsequent
changes.
• Subgrade and drainage characteristics—subgrade
type and the presence of subdrains and edge drains.
• Maintenance history—types and dates of subsequent
pavement M&R treatments, including the age of a current
pavement surface.
• Pavement condition data—includes past and current
data.
• Traffic data—number of aircraft operations and type
of aircraft.
Pavement inventory data are stored in an APMS database,
such as MicroPAVER, that has the capability to graphically
display archived data.
PAVEMENT EVALUATION PRINCIPLES
APMS pavement evaluation includes field measurements of the
current state of pavement characteristics and recording them for
future use. It encompasses the evaluation of pavement surface
distresses, roughness, friction, and pavement strength. The
main principles of airport pavement evaluation include:
13
• Objectivity and consistency—Objective and consistent pavement evaluation produces true trends and provides reliable data for pavement investment decisions.
Objectivity and consistency of repeated evaluations
enables airport owners to see how the pavement conditions change over the years. They also enable funding
agencies to compare pavement conditions of different
airports within and outside their jurisdiction.
• Timelines and relevancy—Pavement evaluations support planning and budgeting cycles and provide data for
timely implementation of pavement preservation treatments, particularly preventive maintenance treatments.
• Long-term monitoring—Historical pavement performance data from repeated evaluations are vital for the
development of pavement performance models used to
estimate when M&R treatments will be needed. Longterm monitoring data also enables evaluation of past
performance of pavement preservation treatments.
• Cost-effectiveness—Collection of pavement evaluation
data in the field can be expensive. The type, amount, and
the frequency of data collection are affected by costeffectiveness considerations.
• Frequency of evaluation—Public Law 103-305 (1994)
states that if an airport is conducting a PCI assessment as
part of pavement management activities, a 3-year inspection cycle is sufficient. However, the 3-year cycle may be
too long for selecting and implementing preventive maintenance treatments in a timely manner.
• Network- and project-level evaluation—There is a
difference between pavement evaluation data at network and project levels. Network-level management
entails periodic surveys of pavement surface distresses
and pavement friction on sample units. Project-level
pavement management typically involves detailed evaluation of pavement surface conditions over the entire
project area and the evaluation of pavement load capacity through nondestructive testing (e.g., deflection, cone
penetrometer, and ground penetrating radar) and destructive testing (e.g., coring and boring and subsequent
material testing).
EVALUATION OF PAVEMENT CONDITION
The following pavement characteristics are evaluated for inservice airfield pavements
•
•
•
•
•
Pavement surface distress
Pavement roughness
Pavement friction
Presence of foreign object debris
Pavement structural strength or capacity.
Pavement Surface Distress
Surface distresses of airport pavements are typically evaluated using the PCI. The PCI evaluation methodology was
developed by the U.S. Army Corps of Engineers and is
described in FAA Advisory Circular on Guidelines and Procedures for Maintenance of Airport Pavements (2007) and in
ASTM Standard D5340 (2003). It is noteworthy that ASTM
adopted the PCI as a pavement condition rating standard for
airfield pavements. The PCI values can range from 0 to 100
and be interpreted as shown in Table 1.
PCI distress data are obtained by a visual survey carried
out by trained pavement evaluators who walk on the pavement. Alternatively, the evaluation can be done by taking highquality pavement images and interpreting them using pavement evaluators or specialized software. The PCI is based on
the evaluation of distress type, severity, and quantity.
• Distress type—There are 16 pavement surface distress
types for AC pavements and 15 for PCC pavements.
Considering pavement preservation needs, prominent
distresses for AC pavements include longitudinal and
transverse cracking, rutting, weathering and raveling,
and block cracking. Also included are two distresses
specifically related to airport operations—jet blast and
oil spillage. For PCC pavements, prominent distresses
include joint seal damage, joint spalling, faulting, corner
break, and linear cracking.
TABLE 1
PAVEMENT CONDITION INDEX FOR AIRPORT PAVEMENTS
PCI Rating
86–100
Description
Good—only minor distresses
Applicable Pavement Preservation
Treatments
Routine maintenance only
71–85
Satisfactory—low and medium distresses
Preventive maintenance
56–70
Fair, some distresses are severe
41–55
Poor—severity of some of the distresses can
cause operational problems
Very poor—severe distresses cause
operational problems.
Serious—many severe distresses cause
operational restrictions
Failed—pavement deterioration prevents safe
aircraft operations
Corrective maintenance and
rehabilitation
Rehabilitation or reconstruction
26–40
11–25
0–10
Rehabilitation and reconstruction
Immediate repairs and reconstruction
Reconstruction
14
• Severity of pavement surface distress—There are four
severity levels defined for most of the pavement distress
types—none, low, medium, and high. The severity rating
is facilitated by a systematic description of the severity
levels and by photographs illustrating the differences
between the levels.
• Quantity of pavement distress—Quantities are measured in feet or in square feet of the affected area.
distress surveys for all airports under their jurisdiction using the
PCI procedure. For example, all 50 public airports in Michigan
are evaluated using the PCI methodology (Michigan Airports
Division 2007).
For project-level analysis, the evaluation of surface distresses typically uses the same rating as that used for the network level. However, the entire section is evaluated instead
of only sample units.
Evaluation Methodology
The distress assessment is done only on selected sample units.
The results for sample units are averaged and the average result
is reported for the entire section. The sample units are of a
uniform size and selected by statistical sampling. The number
of sampling units is chosen to achieve the desired accuracy
and reliability.
The major advantages of the PCI procedure are its wide
use, objectivity, and acceptance. A PCI rating provides a good
indication of the functional serviceability of the pavement and
basic information about its structural integrity. A PCI rating
alone can be used to estimate M&R needs for planning purposes. The advantages as well as potential misconceptions
and pitfalls of using the PCI procedure for airfield pavements
have been described by Broten and De Sombre (2001).
As described in Table 2, 78% of all airports surveyed
carry out periodic PCI surveys on the runways, with an average frequency of every 3.4 years. The PCI surveys are done
even by airports that do not have a formal PMS, and are
sometimes done by state aviation administrations on behalf
of the individual airports. Only one airport used an internal
method to evaluate pavement surface distresses, and 10% of
airports did not carry out any periodic pavement evaluation.
Table 2 also notes that 54% of survey respondents use the
PCI for taxiways and other facilities, with average frequencies of every 3.3 years. Information on the use of other types
of pavement characteristics is also described. In addition,
several airport agencies reported using digital images to document pavement surface distresses.
Most state aviation agencies, such as those in Ohio, Michigan, Washington, Montana, and Oregon, carry out periodic
Roughness
The FAA defines profile roughness as surface profile deviations over a portion of the runway that may increase fatigue
on airplane components, reduce braking action, impair cockpit operations, and/or cause discomfort to passengers. The
interaction between aircraft responses and runway pavement
roughness is complex and depends on the type, weight, and
speed of aircraft, and on the position of the observer in the
aircraft (Woods and Papagiannakis 2009). Traditionally,
M&R actions designed to improve pavement smoothness have
been based on pilot observations and complaints (Larkin and
Hayhoe 2009).
For newly constructed airport pavements, procedures for
measuring and specifying pavement roughness have been
developed and accepted. For in-service pavements, a first
step toward defining and implementing pavement roughness
criteria is provided by FAA Advisory Circular on Guidelines
and Procedures for Measuring Airfield Pavement Roughness
(2009). The roughness criteria presented in the current version of the Circular are intended to address isolated bump
events and do not address cyclic or harmonic events that can
have a substantial impact on airplane occupants, components,
and operations.
The FAA also developed an inertial profiling system for
measuring runway and taxiway longitudinal elevation profiles
and a computer program, Profile Federal Aviation Administration (ProFAA), to analyze the measured profiles. The ProFAA
can be used to compute a variety of airport pavement roughness
indices from the measured profiles, including the Boeing Bump
Index and the International Roughness Index.
TABLE 2
EVALUATION OF PAVEMENT CHARACTERISTICS
Runways
Pavement
Characteristic
PCI
Roughness
Friction
FWD testing
Usage
(%)
78
12
22
18
Average
Frequency, years
3.4
N/A
N/A
3.7
Taxiways and Other Facilities
Usage
(%)
54
4
8
12
Average
Frequency, years
3.3
N/A
N/A
N/A
Based on the survey.
Notes: FWD = Falling Weight Deflectometer; N/A = Data are not available or are insufficient.
15
Based on the survey results, approximately 12% of agencies reported using roughness surveys on runways and 4% of
agencies on taxiways and other facilities (see Table 2).
Pavement Friction
Pavement friction is the force that resists the motion between
a vehicle tire and a pavement surface. Pavement friction is a
significant safety concern for aircraft with greater weight and
landing speeds, such as turbojet aircraft, particularly when
the pavement is wet. The Guide for Pavement Friction (Hall
at al. 2009) provides general technical information on pavement friction.
FAA Advisory Circular on Measurement, Construction,
and Maintenance of Skid-resistant Airport Pavement Surfaces (2004) provides guidelines for designing skid-resistant
airport pavement surfaces and for on-going monitoring and
evaluation of pavement friction. The Circular also describes
recommended procedures to measure pavement friction and
provides specific friction levels required for safe aircraft
operations. These friction levels can be used to plan and carry
out appropriate M&R actions.
For airfield pavements, friction is typically evaluated on
runways only. Twenty-two percent of responding agencies
reported that they evaluate pavement friction on runways. In
addition, 8% of airport agencies reported measuring friction
on taxiways (see Table 2).
Structural Evaluation
The overall structural strength of airport pavements is evaluated using the Aircraft Classification Number–Pavement Classification Number (ACN-PCN) method outlined in the draft
FAA Advisory Circular on Standardized Method of Reporting
Airport Pavement Strength—PCN (2009). The PCN captures
the relative strength of the pavement structure (considering a
standard subgrade) and the ACN provides guidance to airport
operators regarding the relative effect of an aircraft on the
pavement structure. The PCN evaluation is not routinely
used for the planning of pavement M&R treatments and was
not included in the survey.
According to the survey (see Table 2), 18% of airports,
typically large airports, carry out periodic network-level surveys using a Falling Weight Deflectometer (FWD) on runways and 12% of surveyed airports reported FWD surveys of
taxiways and other facilities. The average frequency of the
FWD surveys on runways was 3.7 years.
Procedures for FWD testing are outlined in FAA Advisory
Circular on Use of Nondestructive Testing Devices in the
Evaluation of Airport Pavements (2004). For project-level
analysis, structural evaluation is discussed in chapter seven.
CONDITION ANALYSIS
Pavement condition analysis utilizes pavement condition
data in pursuit of the following outcomes:
Presence of Foreign Object Debris
The presence of foreign object debris is evaluated using the
Foreign Object Damage/Debris (FOD) Index. The FOD
Index is determined from the PCI calculated by considering
only the distresses/severity levels capable of producing FOD
(Pavement Engineering Assessment Standards 2004). The
FOD index is generally not used at major airports.
• Assessment of the overall condition of the pavement network. For example, Figure 7 shows the results of a PCI
survey for a small Michigan airport (Michigan Airports
Division 2007). The objective assessment of the condition of the asset is also useful in meeting the accounting
recommendations of the Governmental Accounting
Standards Board (1999).
TW927 (36)
A01 (34)
RW1533 (34)
THSOUTH (100)
THW (21)
TWA (100)
TWA (100)
TWB (100)
RW1836 (100)
A02 (70)
THEAST1 (29)
RW1533 (34)
THEAST2 (29)
Pavement Condition Index
100 - 86
85 - 71
70 - 56
55 - 41
40 - 26
25 - 11
10 - 0
FIGURE 7 Example of a graphical display of Pavement Condition Index.
16
100
20
All other facilities
0
2005
Runways
2002
40
2008
60
1999
Average PCI
80
well-formed, but before cracks become raveled, have developed into multiple cracks, or before the crack width exceeds
about three-eighths of an inch. Most effectively, condition
surveys of pavement surface distresses for the selection and
timing of preventive maintenance treatments are annually
carried out on candidate pavement sections. The first pavement preservation treatments are typically carried out when
the pavement surface layer is between 3 and 5 years old. The
results of the synthesis survey show that the average frequency
of PCI surveys on runways was 3.4 years (see Table 2) with
the range of from 1 to 10 years.
Survey year
FIGURE 8 Illustration of trends in average PCI for
runway pavements and all other pavements.
• Trends in pavement condition. Historical trends in the
health of the network provide linkage between pavement
preservation investments and the outcomes. For example,
Figure 8 shows an improvement in the condition of the
runway pavements, but no improvement in the condition of pavements on other facilities. The PCI results in
Figure 8 are based on a 3-year evaluation period.
• Documentation of system benefits. Systematic analyses
of pavement conditions play a vital role in the documentation of APMS benefits necessary to secure continued
financial support for the program.
• Documentation of funding needs. Condition analysis
provides basic data for the determination of funding
needs, as described in chapter five.
• Technical analysis of pavement performance. Systematic pavement condition evaluation can identify:
– Major causes of pavement deterioration such as poor
drainage and inappropriate pavement materials.
– Well or poorly performing initial pavement structures, or the subsequent M&R treatments.
– Rates of pavement deterioration for different pavement
types, facilities, and M&R treatments. The deterioration rates are used to develop pavement performance
models discussed in chapter five.
– Pavement sections with inadequate structural capacity.
PAVEMENT PERFORMANCE PREDICTION
For planning purposes, airport pavement maintenance managers estimate future pavement preservation needs. A typical
planning period is 5 years; however, some large airports may
prepare pavement preservation plans for major runways for
up to 15 years. Predicting pavement performance and storing
the results in the APMS database assists managers in identifying future pavement performance.
Use of Pavement Performance Prediction
Future pavement performance, or pavement deterioration, is
estimated using pavement performance models. The survey
revealed that 66% of responding airport agencies use an APMS
to predict future pavement deterioration (see Figure 6). Pavement performance prediction serves the following:
• Estimation of when the pavement will require M&R
treatment. The need for performance prediction is illustrated in Figure 9, which shows pavement performance
curves for two pavements. Both pavements have the
same present PCI, but pavement B deteriorates, and is
expected to deteriorate, faster than pavement A. Consequently, pavement B will require an earlier pavement
preservation treatment.
• Estimation of treatment type. As shown in Figure 9,
when pavement condition reaches a minimum acceptable service level it should be rehabilitated. To identify
Pavement condition surveys that evaluate the type, severity, and
extent of pavement surface distresses are also used in preventive maintenance programs. However, for selection and application of preventive maintenance treatments it is also desirable
to identify specific pavement conditions and early indicators
that trigger the need for preventive maintenance treatments.
Preventive maintenance treatments are best applied when
they are most cost-effective, typically before distresses progress
and more expensive corrective treatments are needed. For
example, treatments to route and seal cracks in asphalt concrete pavements are carried out when the cracks are already
Pavement Condition Index (PCI)
PAVEMENT EVALUATION
FOR PREVENTIVE MAINTENANCE
100
Predicted performance
A
B
Remaining Service
Life
Minimum acceptable
service level
Past performance
0
Now
Now + 2
Pavement age, years
FIGURE 9 Pavement performance prediction.
Now +5
17
•
•
•
•
future funding needs, the type of the M&R treatment,
and its cost and timing, need to be estimated.
Estimation of the life span of M&R treatments. To select
cost-effective treatments, it is necessary to estimate the
cost of the treatment and its life span. The subsequent
monitoring of the treatment performance provides feedback on the choices made.
Deterioration rate. The predicted rate of pavement deterioration can also be used as one of the factors to select
candidate sections for M&R. In Figure 9, pavement B is
expected continue to deteriorate at a higher rate than
pavement A, and the timing of the M&R treatment for
pavement B is now.
Estimation of the remaining service life. Figure 9 also
defines the remaining service life of the pavement. When
known for all sections of the network, the remaining service life can be used to characterize the overall condition
of the network. It is also useful in planning and programming pavement M&R activities (Wade at al. 2007a).
Timing of preventive maintenance treatments. Pavement
conditions that exist at the time of the pavement evaluation survey may need to be extrapolated to the time
when an M&R treatment will be applied. In some cases,
the lead time may be 3 or more years. Preventive maintenance treatments are typically planned only from 2 to
18 months in advance.
Pavement Performance Modeling Techniques
Pavement performance depends on many local factors such
as the type and frequency of traffic loads, environmental exposure, subgrade characteristics including drainage, and pavement structure. Consequently, pavement performance models
are not easily transferable from airport to airport. The selection
of performance models depends on available data, agency
requirements for estimating future pavement preservation
needs, and on the APMS software used.
a few sections with known performances and applied to
all other sections. Family modeling is a default modeling approach in MicroPAVER (Shahin 2001).
• Extrapolation of existing trends. This approach is a
variation on family modeling. If the condition of the
pavement was evaluated on only one previous occasion,
the family pattern is extrapolated taking into account the
condition observed in the past. If the condition of
the pavement was evaluated in the past on more than
one occasion, the extrapolation using a family curve can
take into account the past observation points using
regression analysis.
The extrapolation using one observation point is illustrated in Figure 10. The observed PCI value in year 10 is
above the family prediction curve. Following the trend
established by the family prediction curve it is expected
that the section will reach the minimum recommended
PCI level in year 20, compared with year 18 expected for
the pavement family prediction.
• Markov probability models. Markov models have been
used for pavement performance prediction of highway
pavements. However, it appears that they have not been
used for airfield pavements (Tighe and Covalt 2008).
Artificial neural networks. Artificial neural networks (ANN),
or neural networks, are computing procedures or systems
that can link a large set of data (e.g., a data set describing the
pavement and its exposure to the traffic and environment) to
an outcome (e.g., expected life span of the pavement) without using traditional statistical analysis. However, pavement
performance models, whether they are developed using ANN
or conventional modeling techniques, have to be calibrated
to local conditions. Although the calibration process can be
facilitated using ANN, the calibration of ANN requires specialized computational techniques that are still experimental.
The applicable technology of ANN is reviewed in Transportation Research Circular E-C012: Use of Artificial Neural
Networks in Geomechanical and Pavement Systems (1999).
Typical methods used for pavement performance modeling include:
Pavement Condition Index (PCI)
• Expert modeling. Expert modeling can be used when historical pavement performance data are not available. Performance models, such as a relationship between pavement condition and pavement age for different pavement
types (e.g., AC or PCC) and airport pavement facilities
(e.g., runways and taxiways) are based on the expert
opinion of pavement professionals (Zimmerman 2000).
• Modeling using families of performance curves. The
concept of “family” modeling is based on the expectation that similar airport pavements exposed to similar
traffic will perform in a similar way. For example, all
pavement sections on runways that have AC overlays
are expected to have the same pattern of pavement deterioration. The deterioration pattern is established using
100
Observed PCI
80
Section-specific prediction
60
Minimum recommended PCI level
40
Pavement “family”
prediction
20
0
0
5
10
15 18 20
Pavement age, years
25
FIGURE 10 Pavement performance prediction using a
pavement family prediction.
30
18
CHAPTER FOUR
TECHNOLOGY OF PAVEMENT PRESERVATION TREATMENTS
This chapter describes the technology of pavement M&R
treatments for AC and PCC pavements. It also describes the
survey results concerning the use and performance of M&R
treatments reported by airport agencies.
SURVEY RESULTS
Survey results for AC and PCC pavements are summarized
in Tables 3 and 4, respectively. The tables contain information on the usage and performance of common M&R treatments as reported by 50 representatives of airport agencies.
There were 19 M&R treatments included in the survey for
AC pavements (Table 3) and 19 M&R treatments for PCC
pavements (Table 4). The treatments traditionally considered
to be preventive maintenance treatments are shown in Tables 3
and 4 in italic font.
Data presented in Tables 3 and 4 are the percentages of
usage or performance of M&R treatments reported by survey
respondents. For example, referring to the first row of data in
Table 3, 84% of airports that responded to the survey routinely
use crack sealing with hot-poured sealant and 11% of airports
have tried using this treatment. Consequently, 95% of the airports routinely use or have tried using this treatment and the
remaining 5% have not. Continuing with the example data in
the first row, 19% of the airports that routinely use or have tried
using crack sealing with hot-poured sealant reported very good
performance with this treatment, 71% of the airports reported
good performance, and 10% of the airports reported poor performance. The number of reporting airports, corresponding to
the percentages of airports given in Tables 3 and 4, are presented in Appendix A as part of the Survey Questionnaire.
Approximately 70% of the responding airports had both
AC and PCC pavements on at least some airfield facilities,
and about 30% of airports had both AC and PCC pavements
on runways (Figure 11). Approximately 50% of airports had
only AC pavements on runways and 20% of airports had only
PCC pavements on runways. Considering the distribution of
pavement types, a large segment of airports need to have staff
familiar with the technology of both AC and PCC pavements.
Use of Maintenance and Rehabilitation Treatments
Information on the use of M&R treatments obtained from the
survey provides a good indication of what types of such treat-
ments are used across the country. For example, 84% of airports (that have AC pavements) reported that they routinely
use crack sealing with hot-poured sealant (Table 3). Similarly, 61% of agencies (that have PCC pavements) reported
that they are routinely using, or have tried using, joint sealing with silicone sealant (Table 4).
The use of some M&R treatments depends on the size and
volume of traffic of the airport, such as the treatments aimed
at increasing pavement friction. Consequently, although about
39% of the responding airports reported using diamond grinding (routinely or on a trial basis), the percentage for small airports would probably be considerably lower, and for large
airports most likely considerably higher.
For AC pavements, the following six M&R treatments
were used by less than 15% of agencies that had AC pavements on at least one facility: spray patching, texturization
using fine milling, microsurfacing, hot and cold in-place
recycling, and PCC overlay.
For PCC pavements, the following four M&R treatments
were used by less than 15% of the agencies: load transfer
restoration treatments using sub-sealing and slab stitching,
full-depth repairs using precast panels, and microsurfacing.
Performance of Maintenance
and Rehabilitation Treatments
Survey results concerning the performance of M&R treatments reported in Tables 3 and 4 are not reliable because of
sample size limitations and the lack of objective guidelines
for the evaluation of treatment performance. A very large
sample size would be needed to obtain a statistically significant number of performance reports for the M&R treatments
that are not frequently used, even if all survey responses were
grouped in one sample. However, the treatment performance
may depend on the environmental zone (e.g., wet-freeze,
dry-freeze, dry-no freeze, and wet-no freeze) and on the airport facility (runway, taxiway, and apron) further increasing
the sample size.
To obtain an objective rating of the treatment performance shown in Tables 3 and 4 would also require the development of performance evaluation guidelines for all M&R
treatments and adherence to such guidelines by the respon-
19
TABLE 3
PAVEMENT PRESERVATION TREATMENTS FOR ASPHALT
CONCRETE PAVEMENTS
Survey Result, %
Usage
Performance
Very
Good
Good
hot-poured sealant
84
11
95
19
71
10
cold-applied sealant
9
7
16
17
66
17
hot mix
52
16
68
42
58
0
cold mix
43
18
61
13
50
37
proprietary mix
9
11
20
25
50
25
Poor
Total
Small area (pothole)
patching using
Have
Tried
Crack sealing with
Routine
Treatment Type
Spray patching (includes manual chip seal)
5
7
11
0
100
0
Machine patching with AC
27
14
41
39
55
6
Milling and machine patching with AC
0
34
18
52
39
61
fine milling
7
5
11
20
80
0
controlled shot blasting
0
16
16
0
71
29
Rejuvenators, fog seals, etc.
30
23
52
23
59
18
Surface treatment
15
18
43
6
81
13
Slurry seal
23
25
48
10
75
15
Microsurfacing
2
9
11
25
75
0
Hot-mix overlay
45
23
68
48
48
4
Milling and hot-mix overlay
45
18
64
58
42
0
Hot in-place recycling
5
2
7
N/A
N/A
N/A
Cold in-place recycling
2
0
2
N/A
N/A
N/A
Whitetopping (PCC overlay)
7
7
14
60
20
20
Texturization using
Notes: Treatments traditionally considered preventive maintenance treatments are in italics.
N/A: sample size is too small.
dents. For example, evaluation guidelines would need to be
prepared to explain what conditions need be met to rank the
performance of an overlay as very good. Several respondents
did not provide performance ranking for treatments that they
do not use routinely, and some respondents were reluctant to
provide any ranking at all. Nevertheless, the performance
information obtained from the survey provides information
on overall trends.
routinely use or tried making shallow repairs of PCC slabs
using PCC material or AC material. It is generally recommended that PCC material be used to repair PCC slabs. This
recommendation is supported by the performance data given
in Figure 12. As expected, the survey data show somewhat
better performance of PCC material.
Average performance data from the survey respondents
for both AC and PCC pavements are presented in Table 5.
There is only a very small, statistically insignificant difference between the average performance of M&R treatments
for AC pavements and those for PCC pavements. For example, on the average, the performance of approximately 60%
of M&R treatments for AC pavements was rated as good,
whereas the corresponding number of M&R treatments for
PCC pavements was about 58%. On average, only about
11% of M&R treatments for AC pavements received a poor
performance, whereas the corresponding percentage for PCC
pavements was 12.
In addition to the common M&R treatments listed in Tables 3
and 4, airport agencies reported the use, and in some cases
commented on the performance, of the following innovative
M&R treatments:
For frequently used treatments, it is possible to identify
some expected trends in the performance of M&R treatments. For example, approximately 50% of airport agencies
Innovative and Additional Treatments
• Stress-relieving membranes to retard reflective cracking in AC overlays.
• Proprietary materials for AC overlays.
• Portland cement with high proportions of fly ash and
blast furnace slag.
• Rejuvenators (asphalt emulsions) to stabilize granular
shoulders.
• Over-band method of sealing cracks in AC pavements
with sealing material containing fibers.
• Slurry seals containing thermoplastic coal-tar (fuelresistant) emulsion.
20
TABLE 4
PAVEMENT PRESERVATION TREATMENTS FOR PORTLAND CEMENT
CONCRETE PAVEMENTS
Survey Result, %
Usage
Performance
Joint/crack sealing
with
Poor
Good
Very
Good
Total
Have
Tried
Routine
Treatment Type
bituminous sealant
29
15
44
13
80
7
silicone sealant
39
22
61
29
71
0
neoprene seal
7
22
29
36
36
27
2
5
7
N/A
N/A
N/A
Load transfer restoration sub-sealing and slab
jacking
slab stitching
2
5
7
N/A
N/A
N/A
dowel retrofit
12
5
17
60
40
0
PCC
34
15
49
28
67
6
AC
29
20
49
18
65
18
proprietary mix
17
17
34
42
42
17
PCC
AC
proprietary mix
precast panels
46
20
7
2
15
39
17
2
61
59
24
5
47
31
30
N/A
47
54
50
N/A
6
15
20
N/A
Machine patching with AC
5
12
17
33
50
17
Diamond grinding
5
34
39
21
79
0
Controlled shot blasting
0
15
15
0
80
20
N/A
Shallow patch repair
using
Full and partial depth
repairs or slab
replacement using
Microsurfacing
0
5
5
N/A
N/A
AC overlay
10
27
37
36
64
0
Bonded PCC overlay (whitetopping)
7
7
15
40
40
20
Notes: Treatments traditionally considered preventive maintenance treatments are in italics.
N/A: sample size is too small.
Percentage of respondents
80
Only AC
Only PCC
• Fuel-resistant AC containing resin-modified asphalt
cement.
• Warm-mix AC (rather than the traditional hot mix).
• Transverse grooving of AC pavement surfaces to improve
pavement friction.
• Specific repairs of wide or deteriorated pavement cracks
in AC pavements.
• Various types of fog seals.
• Crack filling AC mixes (mastic) for repairs of large
cracks in AC pavements.
• Proprietary AC and PCC mixes for patching repairs.
AC & PCC
60
40
20
0
All facilities
Runways only
Facility type
All of these M&R treatments and materials require continuing evaluation to document cost-effectiveness.
FIGURE 11 Distribution of pavement types.
TABLE 5
AVERAGE PERFORMANCE OF M&R TREATMENTS
FOR DIFFERENT PAVEMENT TYPES
Average Performance for all Treatments
and Airports (%)
Pavement Type
No.
of
Airports
No.
of
Treatments
Very Good
Good
Poor
AC Pavements
44
19
30.2
59.1
10.7
PCC Pavements
41
19
29.6
58.1
12.3
21
Percentage of responses
80
AC material
a Catalog of Airport Pavement Preservation Treatments provided in Appendix B.
PCC material
60
Some of the treatments listed in Tables 3 and 4 can be
applied, with only very small modifications, to both AC and
PCC pavements; for example, microsurfacing, and controlled
shot blasting. Other treatments listed in the tables are just a
variation of the same treatment using different materials. An
example for AC pavements would be the crack sealing of
such pavements with hot-poured sealant versus cold-applied
sealant. An example for PCC pavements would be the shallow
patch repair using PCC material versus using AC material or
proprietary material.
40
20
0
Very good
Good
Performance rating
Poor
FIGURE 12 Performance of materials used for
shallow patch repairs of PCC slabs.
CATALOG OF AIRPORT PAVEMENT
PRESERVATION TREATMENTS
There is a large amount of information available concerning the technology of pavement preservation treatments.
For example, there are literally dozens and in some cases even
hundreds of reports on each of the 38 M&R treatments listed
in Tables 3 and 4. To present information in a concise and systematic way, each of the 38 M&R treatments was described
using the same structure in less than three pages. The result is
For survey purposes, treatments common to both pavement
types, as well as treatments that differ only by the material
used, were considered separately because the usage and performance of these treatments may differ. For the description in
the Catalog the treatments used in the survey were combined
into generic categories based primarily on the construction
technology of the treatments. As a result, the 38 treatments
listed in Tables 3 and 4 were combined into the 24 treatments
listed in Table 6 and are described in the Catalog of Airport
Pavement Preservation Treatments (Appendix B).
TABLE 6
AIRPORT PAVEMENT PRESERVATION TREATMENTS INCLUDED IN THE CATALOG
Both Pavement Types
Texturization using controlled
shot blasting
Diamond grinding
Microsurfacing
3 treatments
Asphalt Concrete
Sealing and filling of cracks (with
hot- or cold-applied sealants)
Small area patching (using hot mix,
cold mix, or proprietary material)
Spray patching (manual chip seal or
mechanized spray patching)
Machine patching with AC material
Rejuvenators and seals
Texturization using fine milling
Surface treatment (chip seal, chip
seal coat)
Slurry seal
Hot-mix overlay (includes milling
of AC pavements)
Hot in-place recycling
Cold in-place recycling
Ultra-thin whitetopping
12 treatments
Portland Cement Concrete
Joint and crack sealing (with
bituminous, silicone, or
compression sealants)
Partial-depth repairs (using AC,
PCC, or proprietary materials)
Full-depth repairs (using AC,
PCC, or proprietary materials)
Machine patching using hot mix
Slab stabilization and slabjacking
Load transfer
Crack and joint stitching
Hot-mix overlays
Bonded PCC overlay
9 treatments
22
CHAPTER FIVE
IDENTIFICATION OF NEEDS
The identification of pavement preservation needs described
in this chapter is based on the results of pavement condition
surveys, the prediction of pavement deterioration, and the
desirable level of service for airfield pavements (Unified
Facilities Criteria on Pavement Maintenance Management
2004). The concept is simple: pavement preservation needs
arise when the predicted pavement condition is lower than
the recommended or mandated level-of-service criteria. The
key for the successful operation of this model is the objective
assessment of pavement condition and the establishment of
the levels of service that are accepted or mandated by decision makers.
LEVELS OF SERVICE AND TRIGGER LEVELS
Pavement preservation needs depend on the level of service
the airport pavements are expected to provide. A higher level
of service, for the same pavement structure, results in higher
M&R needs and thus in higher agency costs. Levels of service for airport pavements are typically expressed in terms of
PCI values. They are seldom expressed in terms of pavement
roughness because of the unavailability of recognized roughness criteria for in-service airport pavements (Larkin and
Hayhoe 2009). However, the FAA is developing new guidelines on roughness of in-service airport pavements as discussed in chapter three.
dated level of service. In other words, the pavement preservation needs become justified and mandated on the basis of
approved criteria.
The levels of service given in Table 7 are example levels
and are included herein for a medium-sized general aviation
airport for illustrative purposes only. It is noted that levels of
service in terms of PCI depend on several factors:
• Airport type and size—General aviation airports may
have lower target levels of service than carrier airports,
particularly large carrier airports.
• Facility type—Higher target levels of service are typically required for runway pavements than for pavements on taxiways or aprons. Also, some airports may
use higher target levels of service for primary facilities
(e.g., primary runways) than for secondary or tertiary
facilities.
• Number of aircraft operations and aircraft size—Higher
target levels of service are typically required for facilities serving a larger number of aircraft operations or
larger and heavier aircraft.
• Pavement type—Some agencies use different levels of
service for different pavement types (Utah Continuous
Airport System Plan 2007).
Minimum Acceptable Level of Service
Level of Service
There are several types of level of service that may be used
to establish the amount of maintenance and rehabilitation airport pavements may require.
Target Level of Service
The target or the desirable level of service can be expressed
only as an average condition of all pavement sections for a
given airport facility. The target level of service is specified
for different facility types because all facilities do not require
the same target level of service. An example is provided in
Table 7. For comparison purposes, this table also includes
the minimum acceptable level of service, which is discussed
subsequently. If the target level of service is approved and
mandated by the airport management it can be used to determine the pavement preservation strategy to provide the man-
The minimum acceptable level of service can be expressed as
the average condition for all sections for a given facility type
or as the minimum acceptable level of service for individual
pavement sections (see Table 7). The sections at or below
this minimum acceptable level of service are slated for M&R
at the first opportunity. The establishment of the minimum
acceptable levels of service also provides rational justification for pavement maintenance and rehabilitation needs. The
minimum acceptable levels of service are also called critical
levels or critical PCI values.
Safety-related Level of Service
The safety-related level of service is typically defined in
terms of minimum recommended friction levels for runway
pavement surfaces given in FAA Advisory Circular on Measurement, Construction, and Maintenance of Skid-resistant
Airport Pavement Surfaces (2004). The safety-related level
23
TABLE 7
EXAMPLE LEVELS OF SERVICE FOR A MEDIUM-SIZE GENERAL AVIATION AIRPORT
WITH AC PAVEMENTS
Facility Type
Level of Service
Average PCI for all Sections
Target or desirable
Minimum acceptable
Minimum Acceptable Level of
Service
PCI for Individual Sections
Runway
80
65
Taxiway
70
60
45
Apron
70
60
40
of service can also be defined in terms of other pavement surface defects such as rutting depth.
55
ment M&R treatments is shown in Table 8. The relationship
shown in this table, developed for all key pavement distresses, is called a maintenance policy in MicroPAVER.
Trigger Levels
IDENTIFICATION OF NEEDS
In addition to using levels of service to estimate the need for
pavement M&R, trigger levels provide timing guidance for
pavement M&R treatments. An example of levels of service
and trigger values is provided in Figure 13. Trigger values
may be general or treatment specific.
General Trigger Levels General trigger levels provide
guidance on what types of M&R treatments are considered
for a given pavement condition. For example, MicroPAVER
enables the user to specify the PCI levels that trigger a rehabilitation treatment.
Treatment-Specific Trigger Levels These trigger levels are
related to the need to apply a preservation treatment at the
right time to be effective, before the pavement reaches a condition where a different, more expensive treatment would be
needed. For example, sealing of cracks in AC pavements is
most effective when the pavement is still in very good condition. An example of a trigger level for crack sealing and for
an overlay is shown in Figure 13.
Closely related to the concept of trigger levels is the linkage between specific pavement surface distresses and the recommended pavement M&R treatments. An example of the
linkage between pavement cracking and recommended pave-
Pavement Condition Index, PCI
100
Performance curve
Trigger level for crack sealing
Target level of service for average network condition
Identification of needs on the network level consists of the
following four steps:
1. Identification of pavement sections that require M&R
treatments because of the level-of-service requirements or because of trigger levels.
2. Selection of M&R treatments for the sections identified in step 1.
3. Estimation of the costs for the implementation of
M&R treatments selected in step 2.
4. Prioritization of projects if the cost of the treatments,
estimated in step 3, exceeds the available budget. The
selection and prioritization of projects is done systematically and objectively using the procedures described
in the next chapter.
Identification of needs is discussed separately for two
time horizons:
• Short-term planning for time horizons of about 5 years
or less. For simplicity, it is also assumed that the analytical procedures used for short-term planning do not
include the generation and evaluation of alternative treatments in future years.
• Long-term planning for time horizons of more than 5
years. In this case, analytical procedures can include the
generation and evaluation of alternative treatments in
future years.
Short-Term Planning
Trigger level for overlay (mill and fill)
Minimum acceptable level of
service for individual sections
0
Pavement age, years
FIGURE 13 Example of levels of service and trigger levels.
Many airports use short-term planning to identify and prioritize pavement M&R needs. The typical procedure consists
of the following steps:
a) Updating Pavement Inventory—Pavement inventory,
including pavement condition, is updated. The update
includes results of all recent pavement-related projects
and other changes to the pavement infrastructure.
24
TABLE 8
EXAMPLE OF MAINTENANCE POLICY FOR CRACKING
Recommended Maintenance Treatment
Severity of Pavement
Cracking
AC pavements
PCC pavements
Low
None—continue to monitor
None—continue to monitor
Medium
Crack routing and sealing
Crack sealing
High
Crack repairs
Full-depth repairs
b) Defining Scope of Work—Pavement preservation
treatments that can be planned at least a year in advance
are included, whether corrective maintenance, preventive maintenance, or rehabilitation treatments. The treatments may include, for example, sealing of cracks and
joints, AC overlays, full-depth repairs of PCC pavements, and installation of subdrains.
c) Reviewing Pavement Preservation Needs for Each Airport Pavement Section—One of the reasons for dividing
a pavement network into sections is to create future
pavement repair units. Each section is considered in turn
to decide if the section is expected to require any M&R
work during the next 5 years, or during the given planning horizon. Many sections may not require any treatment during the planning horizon, whereas other sections may require preventive maintenance or other types
of treatments. The decisions are based on the mandated
levels of service (Table 7) and trigger values such as
those shown in Figure 13. The needs take into account
expected pavement deterioration during the planning
period. The identification of needs is documentation of
the needs that are necessary on the basis of the levels of
service.
An example of pavement preservation needs for a
small airport (shown in Figure 7) is given in Table 9.
Table 9 was generated by MicroPAVER. In this example, the costs of the major M&R treatments depend on
the PCI levels. The actual type of M&R treatments is
not defined.
d) Selecting Treatment Types—To refine the cost estimates, airport pavement maintenance managers select
the M&R treatment. Figure 14 provides a summary of
survey responses regarding the methods used for the
selection of M&R treatments. For example, about 85%
of respondents use engineering judgment and 30% of
the respondents use computer-based tools. Decision
trees were used by about 6% of the respondents. However, engineering judgment often includes reasoning
that has the structure of decision trees.
The need for maintenance treatments, particularly
preventive maintenance treatments, is determined using
trigger values for individual pavement surface distresses. For example, using the PCI pavement distress
evaluation terminology, the occurrence of joint seal
damage at the medium or high severity triggers the
need for joint sealing, and the occurrence of corner
break at the medium or high severity levels triggers the
need for full-depth patching with PCC. An example of
the network-level maintenance plan generated by
MicroPAVER for the small airport shown in Figure 7
is shown in Table 10. The exact extent of maintenance
work is determined on the project level. For example,
the existence of the 11 corner breaks was estimated by
sampling (and not by an actual field count) and verified
by a detailed survey on the project level. Similarly, the
size of the full-depth patches to repair the cracks needs
to be determined individually for each crack repair.
For localized M&R treatments, MicroPAVER uses
maintenance polices that match the distresses with
M&R treatments (Table 8). Major M&R treatments are
identified as a function of the PCI level in terms of costs
only (Table 9). Other software packages identify generic
TABLE 9
EXAMPLE OF 2009 5-YEAR MAJOR M&R PLAN FOR UNLIMITED BUDGET
Plan
Year
2009
Branch
Name
A01
Section
Number
10
20
THEAST
10
RW1533
10
2010
No work identified
2010
No work identified
etc.
5-year plan total
Source: Michigan Airports Division (2007).
Section
Area, ft2
48,000
46,000
17,800
205,600
Maintenance, $
0
49,400
0
0
Major
M&R, $
238,000
0
97,100
945,900
Cost, $
238,000
49,400
97,000
945,900
49,400
1,794,700
1,844,100
25
Percent of respondents
Percent of respondents
100
75
50
25
60
40
20
0
Yes
Have dedicated
preventive
maint. budget
Identification of preventive maintenance treatments
Co
m
pu
En
te
rp
gi
ne
ro
gr
er
am
in
g
W
ju
or
d
st
gm
co
en
nd
t
iti
on
D
f
irs
ec
t
isi
W
on
he
tre
n
ha
es
za
rd
A
e
ge
xi
sts
of
O
pa
pe
ve
ra
tio
m
en
na
t
O
l
th
p
r
er
io
rit
co
ie
ns
s
id
er
at
io
ns
0
• What will be the condition of the pavement network
10 years from now given the existing budget?
• What is the future funding to achieve a specified level
of service?
• How much additional funding will be needed in the
future to compensate for reduced funding now?
• What would be the impact on the network condition of
diverting funds to preventive maintenance or lowercost treatments?
• What would be the impact of constructing new runways
or taxiways on the pavement preservation budget?
FIGURE 14 Methods used to select M&R treatments
on the network level.
Long-Term Planning
Long-term planning for airport pavement maintenance needs
can improve engineering and economic decision making by
helping answer the following example questions:
No
FIGURE 15 Systematic identification of preventive
maintenance needs.
Selection of treatments
treatment types; for example, an AC overlay, and the
corresponding cost of the generic treatment types. The
actual treatment design, including the design of preoverlay improvements, overlay thickness, and material
properties, is done on the project level.
e) Selection of Preventive Maintenance Treatments—
About 56% of airports systematically identify pavements that would benefit from preventive maintenance
and 35% of airports do so when budget permits (Figure
14). For comparison purposes, Figure 15 also shows that
33% of airports have dedicated budgets for preventive
maintenance. The existence of a dedicated budget for
preventive maintenance is considered to be one of the
prerequisites for timely, successful, and sustainable operation of preventive pavement maintenance programs.
Budget
permitting
The accuracy of future funding requirements for airport
pavement maintenance depends on the reliability of longterm prediction of pavement performance and the generation
of feasible alternatives. Long-term planning and prioritization can consider, for each section, several treatment options
in each analysis year. This results in a large number of possible combinations of program years and treatments for one
section alone.
The concept of generating alternative M&R treatments
for different years is illustrated for one pavement section in
Figure 16. For clarity, only two treatments (microsurfacing
and overlay) and two analysis years (now-plus-3 years and
now-plus-9 years) are considered. Alternative 1 is microsur-
TABLE 10
EXAMPLE MAINTENANCE PLAN
Pavement Surface Distress
Branch
Name
A01
Total
Section
No.
20
Type
Severity
Quantity
Unit
Maintenance Treatment
Cost
Corner
break
Linear
cracking
Joint seal
damage
Shattered
slab
Corner
spalling
High
11
Slab
Full-depth patching with PCC
$9,500
Medium
150
Feet
Crack sealing
$400
High
460
Slab
Joint sealing
$34,000
High
4
Slab
Full-depth patching with PCC
$4,700
High
12
Slab
Partial-depth patching with
PCC
$800
$49,400
26
Micro-surfacing
Overlay
100
Pavement Condition Index
1
2
Minimum acceptable service
level
0
Now Now + 3 Now + 9
Pavement age, years
FIGURE 16 Pavement performance prediction for
multi-year identification of needs.
facing to be constructed 3 years from now. Alternative 2 is
an overlay to be constructed in year now plus 9 years, when
the existing pavement will reach the minimum acceptable
level of service.
Sophisticated software generates and evaluates multiple
treatment options. For the example shown in Figure 16 it
means generating the two alternative treatments (microsurfacing and overlay) at two different years, and estimating
their life spans. The life spans of the alternatives and their
costs are used subsequently to select the most cost-effective
alternative. This type of analysis has been carried out by
many highway agencies, but is not routinely done by airport
agencies.
27
CHAPTER SIX
PRIORITIZATION, PLANNING, AND BUDGETING
This section outlines how M&R needs are prioritized, scheduled for implementation through programming, and then
molded into a budget for a CIP (Wade et al. 2007b). Also
described is the computer software that facilitates the identification of M&R needs and prioritization.
The listing of all M&R needs, such as those shown in
Tables 9 and 10 in chapter five, represent an unlimited budget.
The unlimited budget will change for the following reasons:
• Economic considerations. Not all M&R treatments can
be carried out to the extent and at the time recommended by the unlimited budget because of financial
constraints.
• Operational considerations. Scheduling of the projects
avoids interfering with airport operation. It is particularly
important for scheduling work on runways and taxiways
that provide service that cannot be picked up by alternative facilities. Other operational concerns include safety
issues, airlines’ operations, and allowable closures.
• Other construction work. Pavement preservation work
is typically coordinated with other airfield maintenance
and construction activities. For example, during the
replacement of an in-pavement lighting system on a
runway, pavement preservation work can be carried out
on a parallel taxiway.
• Construction capacity. The schedule may need to take
into account capabilities of the local construction industry and the capability of the airport agency to manage
construction work.
PRIORITIZATION
The prioritization of needs is described for the same two scenarios used for the identification of needs—short-term planning and long-term planning.
The first step in the prioritization is the assignment of a
priority level to each M&R treatment on the list of treatments
representing the unlimited budget. The priority level reflects
the main reason why the treatment is recommended for
implementation. The priority levels are related to the levels
of service used to identify M&R needs and include safety,
critical, cost-effectiveness, and target-priority levels.
a) Safety Level Prioritization—The safety priority level is
the highest priority for airport pavement maintenance
and includes M&R treatments that are needed to maintain safe operation of aircraft. In general, this level
includes projects to meet safety and regulatory requirements mandated by the FAA and environmental agencies. In the pavement area, the safety priority level may
include, for example, M&R treatments for an AC section with raveling surface resulting in FOD or a runway
with inadequate pavement friction. Because treatments
in this category are obligatory, it can also include carryover projects (already approved projects and projects
that are in progress and need additional funding).
b) Critical Level Prioritization—The critical priority
level includes M&R treatments that are necessary to
provide or maintain a minimum acceptable level of
service.
c) Cost-effectiveness Level Prioritization—This level
includes projects where implementation timing is
important to achieve cost-effectiveness. Typically, this
level includes preventive maintenance projects, such
as joint resealing, carried out before more significant
damage occurs. Approximately 29% of the responding
airports indicated that they implement preventive
maintenance treatments at the right time, and about
57% of airports noted that they sometimes implement
preventive maintenance treatments at the right time
(Figure 17).
d) Target Level Prioritization—Target level includes projects to maintain or achieve the target level of service.
Prioritization for Short-Term Planning
Short-term planning supports only limited prediction of
future network conditions without considering alternative
future pavement conditions resulting from M&R treatments.
The historical and predicted condition of the pavement network can be used to evaluate the adequacy of different pavement preservation budgets. It is also possible to use the backlog of projects as an indication of desirable funding levels.
Projects that belong to the critical level and apply to runways would have higher priority than projects that belong to
the cost-effectiveness level and apply to taxiways.
It is easier and preferable to prioritize projects that belong
to the same priority level and functional class than to prioritize projects across priority levels and functional classes. Prioritization across functional classes, for the same priority
Percent of respondents
28
tiveness and the net present value—defined in the section on
Prioritization for Long-Term Planning.
60
40
Inclusion of Preventive Maintenance
20
0
Yes
Sometimes
No
Implementation of preventive maintenance
FIGURE 17 Implementation of
preventive maintenance treatments at
the right time.
level, can be facilitated by developing priority rankings of
the type shown in Table 11. The highest ranking, in this simplified example, is assigned to runways serving a high number of aircraft operations.
Prioritization can be based on a single characteristic such
as PCI or on a composite indicator that combines the influence of several characteristics.
An example of prioritization of M&R treatments for 271
pavement sections using a composite priority indicator was
provided by Tighe et al. (2004). The composite priority indicator combines the influence of four factors:
1. PCI of the section. This factor represents pavement
characteristics and was assigned the highest weighting. In general, other pavement characteristics that can
be used include a friction index and FOD potential.
2. Number of annual aircraft departures taking off from
the section. This factor represents volume of aircraft
movements and can be alternatively represented by,
for example, the total number of aircraft operations.
3. Functional class of the section (runway, taxiway,
apron).
4. Operational importance of the section (primary, secondary, or tertiary). For example, a runway may be primary or secondary; an apron may be primary, secondary, or tertiary.
Another factor that can be incorporated into a composite
priority indicator is cost-effectiveness—the ratio of effec-
Preventive maintenance reinforces the concept of the right
treatment on the right pavement at the right time. According
to the survey, about 29% of agencies reported that they
implement preventive maintenance treatments at the right
time (see Figure 17). For comparison, a 1999 survey of state
transportation agencies, carried out by the AASHTO Pavement Preservation Lead State Team (2000), reported that
85% of the 41 agencies that responded to the survey have
established a preventive pavement maintenance program.
Systematic implementation of preventive maintenance treatments may represent a shift in the way the pavement preservation is done. The selection of sections for M&R is not done
using a worst-condition-first approach, but by selecting sections where an M&R treatment would be most cost-effective.
Often, the most cost-effective treatment is a preventive maintenance treatment. At the same time, agencies still have to
maintain pavements to provide safe operation of the aircraft
and provide a minimum level of service.
A systematic application of a preventive maintenance program for airport pavements has not been well-documented.
Most of the experience has been reported by state highway
agencies as it applies to highway pavements (Geoffroy 1996;
Zimmerman and Wolters 2003). The Foundation for Pavement
Preservation (2001) developed useful guidelines for launching
a preventive maintenance program and outlined the need to
establish the overall strategies and goals of the program.
Prioritization for Long-Term Planning
Multi-year prioritization of alternative treatments is typically
based on cost-effectiveness. Cost-effectiveness is the ratio of
the effectiveness (benefits) and costs for individual M&R
treatments. The cost of the treatment is based on life-cycle
costs as much as possible (Zimmerman et al. 2000). The effectiveness for an airport pavement section can be calculated by
multiplying (1) the area under the pavement performance
curve, (2) the number of aircraft departures, and (3) the area of
the pavement section (Tighe et al. 2004).
TABLE 11
PRIORITY RANKING BY FUNCTIONAL CLASS AND TRAFFIC
Aircraft Operations or Usage
Priority Rank
Functional
Class
Runways
High
1
Medium
2
Low
4
Taxiways
3
5
7
Aprons
6
8
9
29
100
40
Pavement Condition Index (PCI)
Pavement Condition Index (PCI)
Pavement graph for overlay
100
Area
60
Minimum recommended PCI
Area under the performance curve
Area = ½[40 (PCI units) times 12 (years)]
0
0
Now
3
6
9
Age, years
12
15
18
25
Pavement graph for micro-surfacing
Area under the performance curve
60
10
Area
Minimum recommended PCI
Area = ½[(35 times 9) –(10 times 3)]
0
0
Now
3
6
9
Age, years
12
15
18
FIGURE 18 Example calculation of treatment effectiveness.
The area under the pavement performance curve represents the beneficial effect of the pavement condition that is
above the minimum recommended pavement condition as
shown in Figure 18. Figure 18 illustrates the difference in the
area under the performance curve for two alternatives: an
overlay and microsurfacing. For simplicity, it is assumed that
the change of PCI with pavement age is linear.
The number of aircraft departures is used as the measure of
aircraft operations that benefit from the improved pavement
condition. The use of aircraft departures instead of the total
number of aircraft operations accounts for higher pavement
loads during departures.
The area of the pavement section is used to account for
the differences in the length and width of airport pavement
sections. The dimensions of the pavement section are thus
included in the calculation of both the cost and the effectiveness.
Multi-year prioritization analysis need not include projects addressing the safety and critical priority levels, because
these projects are obligatory. Projects addressing the costeffectiveness priority level and the target priority level are
analyzed simultaneously because both are prioritized on the
cost-effectiveness basis. The analysis has the potential to
yield the most cost-effective combination of preventive maintenance projects and other pavement preservation projects.
Projects are selected for implementation using incremental
cost-effectiveness analysis. This facilitates a multi-year projec-
tion of impacts of the selected M&R treatment on the health of
the pavement network. The result of multi-year prioritization
analysis is a prioritized list of pavement preservation projects
for different years that meet specific budget requirements.
Long-term planning and prioritization of needs, incorporating incremental cost-effectiveness analysis, has been successfully implemented by many transportation agencies on
large highway networks (Federal Highway Administration
1996). The implementation for airport networks is still in
initial phases. A clear example of prioritization using costeffectiveness analysis for an airport pavement network is
provided by Tighe et al. (2004). The reasons for slower
implementation include smaller airport pavement networks,
greater importance of operational constraints, and the limitations of existing software.
PROGRAMMING AND BUDGETING
Programming activities move projects from the initiation, prioritization, and budget stages to the design stage and to implementation. Budgeting builds on the results of planning and
programming activities and produces a budget—a financial
document that specifies how the money will be invested in airport infrastructure.
The type of projects included in the airport capital budget
depend on local circumstances. Whereas large airports may
have a budget dedicated solely to pavement preservation,
capital budgets for smaller airports combine all projects con-
cerning airfield infrastructure, and not just pavement preservation projects, to establish CIP. For example, the budget
may also include projects related to the expansion of the airfield pavements, operational improvements, and M&R of
other airfield infrastructure, such as buildings and guidance
systems. Some authorities prepare a combined budget for a
group of airports they manage. The budgeting process is part
of asset management, the process that strives to manage all
airport infrastructure assets together to achieve the efficient
allocation of resources.
Funding Sources
According to the survey results, the majority of airport agencies establish a pavement preservation budget by considering
pavement preservation needs and PCI (Figure 19). The main
source of funding for pavement preservation, as reported by
airport operators, was the FAA (Figure 20). Funding can also
come from state aviation offices and other sources.
The main source of federal funding for airport pavement
preservation is the Airport Improvement Program (AIP)
administered by the FAA. The AIP provides grants for the
planning and development of public-use airports that are
included in the National Plan for Integrated Airport Systems.
For large and medium primary hub airports, the grant covers
75% of eligible costs. For small primary, reliever, and general
aviation airports, the grant covers 95% of eligible costs. Eligible costs include costs of runway, taxiway, and apron construction and rehabilitation, and costs associated with airfield
drainage improvements. The projects must involve more than
$25,000 in AIP funds.
Percent of respondents
In accordance with Public Law 103-305, section 107,
amended Title 49, section 47105, of the United States Code,
the FAA requires that airport owners receiving any grants for
pavement construction or rehabilitation provide assurances
that the airport has implemented an effective Airport Pavement Maintenance Management Program (APMMP). The
features of an effective APMMP are described in FAA Engineering Policy 99-01. This policy, as well as other documents associated with AIP, is available on the FAA website
(www.faa.gov/airports/aip).
100
80
60
40
20
0
Last-year
Based on Preservation
Other
budget
PCI
needs
Establishing budget for pavement preservation
FIGURE 19 Methods used to establish pavement
preservation budgets.
Percent of respondents
30
100
75
50
25
0
FAA
State
Local
Source of pavement preservation funding
FIGURE 20 Sources of pavement
preservation funding.
There is a variety of state funding programs that support airport pavement preservation. In addition, several states, under
the FAA State Block Grant Program, assume the responsibility of administering AIP grants at smaller airports.
Budget Development
Budgeting takes in account engineering and financial concerns, mandatory safety and regulatory requirements, and airport operational concerns. The process of establishing a budget is schematically illustrated in Figure 21. As shown in this
figure, budget development takes into account a number of
needs and considerations, including the following:
• Pavement preservation needs such as mandatory projects based on the safety priority level and prioritized
M&R treatments established through APMS.
• Other airfield needs affecting airport pavements such as
the expansion of the airfield pavement network, safety
and functional improvements, in-pavement lighting,
drainage improvements, and projects involving underground utilities.
Budgetary considerations include the following:
• Financial considerations such as budget constraints in
terms of available funding and the time frame when the
funding is available. Financial considerations may also
dictate staging the project to meet specific completion
dates. It is often advantageous to combine construction
projects to achieve economies of scale. According to
Stroup-Gardiner and Shatnawi (2008), significant cost
savings can be achieved by organizing pavement preservation work into larger contracts. This activity can be
feasible for large airports or for airport agencies that
manage several airports in one geographical area.
• Operational considerations include the impact on airport
operations experienced by carriers and other airport users,
safety concerns during construction, and the importance
of the facility to overall operations (Wade et al. 2007b).
Budget Evaluation
Budget evaluation, within the framework of pavement preservation, examines the relationship between the investment in
31
Needs
Considerations
Pavement preservation needs
• Mandatory projects
• Prioritized preservation needs
Other airfield needs
• System expansion
• Safety and other improvements
• Underground utilities, etc,
Financial considerations
• Budget constraints
• Economy of scale
Budget development
Packaging of projects
Scheduling
Prioritization
Operational considerations
• Impact on airport operations
• Safety of operations
• Importance of facility
Budget formulation and reporting
Budget evaluation
FIGURE 21 Programming and budgeting activities.
• Monitoring pavement performance trends. An example
of monitoring pavement condition in terms of PCI is
shown in Figure 8 in chapter three.
• Monitoring of expenditures. For example, some road
agencies monitor yearly expenditures on pavement preservation in terms of dollars per square yard of pavement.
• Tracking the dollar value of unfunded pavement preservation needs, if any, and yearly changes in unfunded
needs.
• Evaluation of the consequences of different budget levels on the future condition of the pavement network.
The future pavement condition is typically measured in
terms of PCI.
COMPUTATIONAL SUPPORT
Software
Management of the pavement database and the identification
and prioritization of M&R projects requires extensive data
processing using specialized computer software. Many practitioners view APMS as computer-based decision support
systems. There are several pavement management software
products that can be purchased and customized by airport
agencies.
According to the survey, all airport agencies that have an
operational APMS use a software application. About 53% of
airports reported using MicroPAVER, whereas 13% of airports
used other commercial software (Figure 22). MicroPAVER is
a public use PMS application.
Pavement administrators and engineers select the APMS
software based on individual needs, as each PMS package has
different strengths and weaknesses. Because MicroPAVER
was publicly developed and is publicly supported, the following list of advantages and disadvantages of MicroPAVER is
provided only as an example and guidance to the characteristics that can be used to evaluate and select APMS software.
Advantages of MicroPAVER include:
• Long-term support by the FAA and other agencies, and
ongoing enhancements.
• Relatively inexpensive.
• Incorporates ASTM PCI evaluation methodology.
• Highly scalable; used by small and large airports.
• Integrated with GIS platform; for example, enables
graphical representation of pavement condition.
• Dependable pavement performance prediction based on
“family” curves.
• Enables generation of customized reports and exporting
data to other software applications.
• Customized maintenance policy (for stop-gap, preventive, and global).
• Estimates pavement life extension resulting from maintenance treatments.
• Evaluation of different budget alternatives (unlimited
budget, maintain current condition, constrained annual
budget, eliminate backlog).
Percent of respondents
pavement preservation and the resulting condition of the pavement network. It also attempts to quantify the adequacy of the
budget in meeting pavement preservation needs. Budget evaluation tools include the following:
60
40
20
0
MicroPAVER
Other
commercial
software
Type of APMS software
FIGURE 22 Use of APMS software.
In-house
software
Disadvantages of MicroPAVER include:
• Cost of M&R treatments on the network level is based
on PCI range and not on specific M&R treatments that
address root causes of pavement distress.
• Limited optimization features on network level; optimization is based on PCI value and facility types without considering costs and benefits of the individual
M&R treatments.
• Lack of user customization may require longer implementation.
Based on the survey, 47% of APMS software was operated by in-house staff with outside support (Figure 23).
Thirty-three percent of APMS software was operated by inhouse staff, and 20% of agencies use outside consultants to
operate their APMS.
New FAA Software
The FAA is developing airport pavement management software called PAVEAIR to be distributed to airports and airport
engineers for implementation on commercial and general aviation airports. PAVEAIR will be a web-based application for
easy dissemination of information and will allow data for
multiple airports to be made available on a single server connected to the web. The FAA server installed at the FAA
Percent of respondents
32
60
40
20
0
In-house
staff
In-house and
outside staff
Operation of APMS
Mainly
consultants
FIGURE 23 Operation of APMS.
William J. Hughes Technical Center is intended to be a repository for PMS data from PAVEAIR on airport projects funded
under AIP; this will allow the FAA to monitor the performance of AIP projects and gain needed information on variables and materials that impact pavement performance.
PAVEAIR software will be available to users as a free
download and the software will initially be similar to
MicroPAVER in application and operational features. Existing MicroPAVER databases (Micro Paver e60 files and
Micro Paver MDB files) can be imported into PAVEAIR so
that current MicroPAVER users will not lose any existing
data. The first release of PAVEAIR will have the functionality of MicroPAVER Version 5.3. The release of PAVEAIR
is planned for late 2010.
33
CHAPTER SEVEN
PROJECT DESIGN AND IMPLEMENTATION
The final treatment type and associated technical details and
costs are determined at the project level. The project-level
activities discussed in this chapter include project design,
project implementation, and the monitoring of completed
projects. The project design and implementation is an integral part of the airport pavement management process (Haas
et al. 1994).
PROJECT DESIGN
Project design determines the specific treatment type and
design details for the construction of the project, such as layer
types, material properties, and construction details. The
selected M&R treatments address the primary cause of pavement deterioration and not just the distresses seen on the pavement surface during a PCI survey. Compared with the networklevel identification of needs and prioritization, the project-level
design requires additional data and data with greater detail.
For large or complicated projects, the design process consists
of a preliminary design stage and the final design stage. The
preliminary design stage includes: (1) identification of alternatives, (2) design of alternatives, and (3) selection of a recommended alternative. The final design stage includes detailed
design of the selected alternative.
Identification of Alternative Maintenance
and Rehabilitation Treatments
Common M&R treatments for airfield pavements are listed in
Tables 3 and 4 in chapter four, and are described in the Catalog of Airport Pavement Preservation Treatments. Treatments can be used alone or in combination. For example, sealing of longitudinal and transverse cracks in AC pavements
and machine patching with hot mix can be carried out together
with a microsurfacing treatment or an AC overlay. The objective of the identification of alternatives is to ensure that no
viable alternative is overlooked. Alternatives that are not realistic or practical need not be evaluated. There are also situations where there are no alternatives and only one practical
M&R treatment exists.
The generation of M&R alternatives uses similar considerations as those used for the design of M&R treatments. For
brevity, these considerations were combined and are listed
here.
• Facility type and the associated requirements for performance reliability of the M&R treatments.
• Pavement surface quality in terms of surface friction,
roughness, and the potential for FOD.
• Existing pavement condition, surface distresses, and
pavement performance history.
• Construction history and previous experience with a
particular treatment under similar circumstances.
• Physical properties of the existing pavement structure.
For the design of M&R treatments, this may require
coring and boring of the existing pavement structure to
obtain dimensions and material samples, and the use of
a dynamic cone penetrometer.
• Structural pavement strength. For the design of M&R
treatments, the determination of pavement strength (structural support) can be done with pavement deflection testing. A good reference is FAA Advisory Circular on Use
of Nondestructive Testing Devices in the Evaluation of
Airport Pavements (2004).
• Anticipated traffic loads in terms of the number of operations, particularly departures, and the type of aircraft.
• Environmental exposure, such as pavement temperature
extremes, number of freeze–thaw cycles, and exposure
to fuel spills.
• Life-cycle costs.
• Benefits; for example, estimated life span of the treatment and frictional properties of the pavement surface.
• Time of year available for construction.
• Availability of funds, qualified or suitable contractors,
agency staff, and availability of materials.
• Facility downtime (for the current pavement M&R treatment and for subsequent treatments) and associated user
costs.
• Operational constraints and construction phasing
requirements.
Over time, many agencies have developed various technical aides for the selection of pavement preservation treatments
on the network and project levels. Some of the procedures used
on the network level were discussed in chapter five. Good
sources of information are comprehensive pavement maintenance guides developed by state highway agencies mentioned
previously—California (2008), Michigan (1999), Minnesota
(2001), and Ohio (2001). Other notable references include an
FHWA report, Selecting a Preventive Maintenance Treatment
for Flexible Pavements (Hicks et al. 2000; Wade et al. 2007b).
34
location, time, quantities, and the capacity of the local industry, and other factors, project-specific construction costs are
typically used in the evaluation of the M&R treatments.
Design of Alternative Maintenance
and Rehabilitation Treatments
The M&R treatment design enables the analyst to estimate the
project-specific costs and benefits, and other attributes of the
competing treatments. Design considerations were listed in
the previous section. Basic information on the design of M&R
treatments is given in the Catalog of Airport Pavement Preservation Treatments in Appendix B.
The methods used to select the recommended M&R alternative include life-cycle cost analysis, cost-effectiveness
evaluation, and ranking analysis. The ranking analysis method
is the most comprehensive and is typically used for important
projects.
Selection of the Recommended Maintenance
and Rehabilitation Treatments
Life-Cycle Cost Analysis
Candidate M&R treatments are typically ranked by airport
pavement maintenance managers according to their estimated benefits and costs. Estimation of benefits for maintenance treatments are in terms of the extension of pavement
life of the original pavement. This concept is illustrated in
Figure 24.
Life-cycle cost analysis (LCCA) facilitates the selection of
the least expensive alternative. LCCA can incorporate the
costs of not only the initial M&R treatments, but also the subsequent treatments. For example, the installation of retrofitted subdrains may have a beneficial effect on more than one
rehabilitation cycle.
Maintenance treatments, particularly preventive maintenance treatments, do not substantially increase the longevity
of the existing pavement condition as shown in the top part
of Figure 24. The main benefit of a maintenance treatment is
the difference between the life span of the original pavement
with and without the maintenance treatment. For example,
full-depth repairs of PCC pavements may last 15 years or
more, but may extend the life of a specific pavement section
by only 12 years, because the section may fail owing to the
presence and progression of other distresses.
Maintenance treatments, particularly preventive maintenance treatments, postpone more expensive rehabilitation
treatments. However, the cost of maintenance treatments is
paid much sooner than the cost of any future rehabilitation
treatment. The need to pay now rather than later is explicitly
recognized in the LCCA by discounting all costs to their
present value. It is important that the analysis period, the
period for which the costs are included in the analysis, be sufficiently long to take into account all relevant consequences
of alternative treatments. The FHWA publication Life-Cycle
Cost Analysis in Pavement Design (Walls and Smith 1998)
provides a detailed description of the LCCA procedures. The
LCCA methodology has been also used to recommend opti-
Treatment costs include life-cycle costs defined in the
Glossary of Terms. Because construction costs depend on
Pavement Condition Index
Benefits due to a maintenance treatment
100
Pavement performance curve
70
Target level of service
Beneficial life
Extended pavement life due
to a maintenance treatment
0
0
5
10
15
Pavement Condition Index
Benefits due to a rehabilitation treatment
100
Target level of service
70
Beneficial life
Extended pavement life due
to a rehabilitation treatment
0
0
5
10
Pavement age, years
15
FIGURE 24 Benefits for M&R treatments in terms of beneficial life.
20
35
mal timing of preventive maintenance treatments by Peshkin
et al. (2004). A new LCCA guide and software package is
also being developed under Airfield Asphalt Pavement Technology Program Project 06-06.
The methodology of LCCA consists of the following
steps:
• Inclusion of all viable and practical alternative M&R
treatments.
• Determination of agency costs for each alternative. The
agency costs include the initial construction costs and
subsequent M&R costs throughout the analysis period.
• Determination of user costs. Many agencies do not
include user costs in LCCA on the project level, because
user costs are often similar for all alternatives and do
not affect agency budget. However, when construction
of M&R alternatives may have a different impact on
airport operations and revenues, for example because of
the differences in the length of construction, user costs
are included.
• Selection of economic parameters for LCCA in terms of
the discount rate and analysis period.
• Calculation of the net present value of agency costs and
user costs.
• Selection of the alternative. The alternative with the
lowest agency and user costs is the best from the economical point of view.
Cost-effectiveness Evaluation
Cost-effectiveness is the ratio and effectiveness (benefits) to
life-cycle costs. The effectiveness is calculated using a similar procedure as that used on the network level described in
the section on Prioritization for Long-term Planning, with
the additional benefit of using more reliable project-specific
data. On the network level, the effectiveness is calculated by
multiplying the area under the PCI performance curve by the
number of aircraft operations and the surface area of the section. The area under the performance curve, considered to be
a measure of pavement serviceability, is illustrated in Figure 18 in chapter six. On the project level, the number of aircraft operations and the surface area are the same for all alternatives and need not be considered. The cost-effectiveness
method provides an improvement over the LCCA method by
taking into account differences in pavement serviceability
provided by different alternatives.
struction. For this reason, in addition to the LCCA that takes
into account monetary aspects of cost and benefits, a systematic
assessment of other treatment attributes may also be carried out.
For example, consider two alternative rehabilitation treatments for an AC pavement on a runway of a small airport: a
traditional overlay and in-place recycling. In addition to the
LCCA that may favor in-place recycling, it is advisable to
also consider other attributes:
• Effectiveness of the two alternatives. Effectiveness is
defined as the area under the pavement performance
curve (see Figure 18).
• Agency experience with the performance of the alternatives.
• Availability of qualified contractors.
• Reliability of cost estimates, particularly if local contractors are not available to carry out a specific alternative M&R treatment.
• Environmental and sustainability benefits owing to
recycling of AC pavement material in-place.
• Potential for future cost savings if a new, less expensive
rehabilitation method becomes available.
• Compatibility with phased or off-peak construction
requirements.
A step-by-step example of this approach is provided in
Selecting a Preventive Maintenance Treatment for Flexible
Pavements (Hicks et al. 2000). Briefly, the procedure consists of four steps:
1. Selection of relevant attributes that are important to the
customer and the agency. The list of attributes given in
the earlier example is only illustrative and does not
include many other attributes that may be important
for specific alternatives, such as pavement friction,
sensitivity to weather during construction, and availability of quality materials.
2. Assigning relative importance to the attributes using a
rating factor. The total score of 100 is distributed to all
relevant attributes.
3. Scoring each attribute in terms of its importance for the
selection of the preferred treatment. This is accomplished using scoring factors on a 5-point scale, 5 being
very important, and 1 not important.
4. Calculating total scores for all alternative treatments
by summing the product of rating and scoring factors
obtained for all attributes.
PROJECT IMPLEMENTATION AND MONITORING
Ranking Evaluation
Some of the attributes of M&R treatments, such as disruption
of airport operations, previous agency experience with the
treatment, sustainability, or improved pavement friction, cannot be readily quantified in monetary terms. M&R treatments
may also create additional benefits in the form of improved
pavement surface or impose operational constraints during con-
The application of M&R treatments currently considers the
use of appropriate materials, construction methods, and quality control and assurance procedures. Following the trends of
the highway construction industry, many airports use endresult specifications for construction quality control. In addition to quality control and quality assurance procedures, airport operators also use construction warranties. Warranties
36
provide a catch-all provision to ensure basic construction
quality. Warranties are particularly important for pavement
maintenance treatments where the construction materials and
procedures are difficult to specify and enforce.
In addition to the periodic condition evaluation of the
entire pavement network, discussed in chapter four, airports
evaluate periodically specific pavement M&R treatments,
particularly treatments that are not routinely used. This
enables the airport pavement manager to expand, modify, or
discontinue specific treatments based on their documented
field effectiveness. According to data presented in Figure 6 (in
chapter two), only 45% of agencies reported using an APMS
to determine the performance of the past M&R treatments.
37
CHAPTER EIGHT
OPERATION, SUSTAINABILITY, AND ENHANCEMENT
More than 80% of airport agencies surveyed already operate
or are developing an APMS. The average age of the existing
APMS for those airports responding to the questionnaire was
approximately 9 years. The challenge for most of the agencies is not to establish an APMS, but to sustain and enhance
its operation. The focus of this chapter is on sustainability
and enhancements of APMS operations rather than on procedures for establishing APMS.
AIRPORT PAVEMENT MANAGEMENT SYSTEMS
OPERATION AND SUSTAINABILITY
The existing APMS operations and the sustainability of the
APMS are closely linked; a successful operation of the system
is one of the best guarantees of its sustainability. Long-term
sustainability of the APMS is an on-going process that should
be considered during the initial implementation (Broten and
Wade 2004). The following factors contribute to the successful operation and sustainability of the APMS:
• Long-term commitment. Long-term commitment to
the operation of the APMS and adequate financial support by the decision makers are essential. Benefits
obtained from the APMS increase with the length of
time the system is in operation. For example, it takes
several years of pavement condition monitoring to ascertain which pavement M&R treatments work best on the
local level, and to establish pavement deterioration rates.
An acceptance of the APMS across the organization
also requires time.
• Data integrity and timeliness. The APMS database is
the source for obtaining pavement-related data. Current
and objective pavement condition data are catalogued
here for the preparation and updating of CIPs.
• Periodic reporting. The manager of an APMS typically provides periodic reports to decision makers on
the condition of airport pavements and on the anticipated pavement preservation needs. Different versions
of the reports, with different levels of detail and presentation styles, may be desirable for each audience. In
addition to periodic reporting, special reports addressing pavement-related issues such as experience with
new M&R treatments are developed and made available. Regular reporting is essential for documenting the
benefits of operating an APMS.
• Documentation of the APMS process. A user manual
documents the APMS process. Documentation ensures
sustainability and continuity of operation during unexpected staff changes and facilitates the transfer of
responsibilities between staff members and/or between
consultants. Based on the survey, 20% of all APMSs are
operated primarily by outside staff, and 48% of these systems are operated jointly by in-house and outside staff
(see Figure 22).
• Meeting user needs. Universal user needs are monitored and include user-friendly software and the provision for sharing of data and results.
• Permanent APMS committee. Operation of a permanent APMS committee, with representation from all
user groups, can be instrumental in the sustainability and
enhancement of the system (Broten and Wade 2004). One
of the tasks of the committee is to monitor user needs.
• Ongoing improvements. The monitoring of user needs
and follow-up to implement improvements enhances
the system over time. Recent enhancements of APMS
developed to meet user needs discovered during proactive monitoring include:
– Graphical presentation and mapping of data and
results using computer-assisted drafting and GIS,
– Automating pavement condition surveys and using
digital images to document pavement distresses,
– Improving the linkage between an APMS and the
preparation of CIPs,
– Incorporating preventive pavement maintenance
programs,
– Addition of pavement structural analysis to APMS
software, and.
– Providing access to APMS database and software
through the Internet.
• Providing training. Initial APMS implementation
includes staff training. However, staff training, together
with succession planning is part of the ongoing operations. Training, including proficiency testing, is particularly critical for personnel who carry out periodic PCI
surveys.
SYSTEM ENHANCEMENT
In addition to ongoing system enhancements there are situations where a structured comprehensive review of the APMS
operation is beneficial for improving the current practice and
38
ensuring sustainability. The objectives of the review are
twofold:
1. To determine enhancements based on identified user
needs.
2. To determine enhancements that may be beneficial
based on the best appropriate practice (BAP). The BAP
is the desired state of practice that meets the particular
agency’s needs in the most appropriate and efficient
way.
The common methodology used for the systematic assessment of the APMS is the gap analysis. As the name suggests
the analysis is concerned with identifying the difference
between the existing management process and the future
desirable process defined as the BAP. The gap analysis consists of three basic steps:
1. Assessment of the existing APMS activities against
the BAP.
2. Identification of activities where the agency has already
achieved the BAP.
3. Identification of activities and an implementation guide
to improvements to reach the BAP.
The APMS activities that are the subject of the gap analysis can encompass all the main areas of a PMS shown in as Figure 3 or they may focus on specific “weak” areas of the APMS
operation. Formal reviews of PMS operation for highway networks, done by either an outside agency or in-house, are quite
common. For example, Zimmerman (2004) developed a selfassessment tool that helps highway agency personnel to systematically evaluate PMS operations and identify areas for
improvement. The process includes a self-assessment ques-
tionnaire, interviews with the stakeholders, and a technical
review. Smith at al. (2004) used gap analysis to carry out a
number of structured reviews of pavement and highway management systems in several countries. The systematic review
of APMS operations is less common than the reviews of roadway PMS; however, its potential to improve the operations,
introduce needed changes, and sustain the operation is similar
to the roadway PMS.
Another method that can help airports to improve their
pavement management practices is benchmarking. Benchmarking is similar to gap analysis in the sense that it provides
a method for agencies to move from an internal focus to an
external focus in the search for best management practices.
However, as the name suggests, benchmarking seeks to compare the operation of different organizations using objective,
agreed-upon measures. In the airport context, the benchmarking measures include outcomes (e.g., average PCI for
runways) and recourses (e.g., annualized pavement preservation cost per square yard of pavements). A primer and a guide
on benchmarking for highway maintenance were developed
by Booz Allen Hamilton (2003). The application of benchmarking as the means to improve airport pavement maintenance practices can be used as part of the gap analysis. In the
context of airport pavement management, the information on
the use of gap analysis and benchmarking is lacking.
It is expected that the new FAA APMS software,
AIRPAVE, now under development, will enhance APMS
technology in two significant ways: (1) it will make the PMS
data readily available to users through the Internet, and (2)
it will be a linchpin linking all main FAA pavement software applications.
39
CHAPTER NINE
CONCLUSIONS
There is extensive literature on the subject of airport pavement
maintenance and rehabilitation (M&R) technology, including
the technology of pavement preservation treatments. However, the information is dispersed and not always current. Airport pavement maintenance practices generally follow the
objectives, management principles, and methodology of roadway pavement management practices. Airfield and roadway
pavements are built and maintained using the same construction technology, materials, and methods. Also, airport and
roadway pavement management systems frequently use similar pavement management software.
All types of pavement preservation treatments, including
maintenance treatments, preventive maintenance treatments,
and rehabilitation treatments, are considered together when
developing pavement preservation strategies for individual
pavement sections and for Capital Improvement Programs.
Preventive maintenance has a special standing in the area of
pavement preservation. The preventive maintenance program
has the potential to improve cost-effectiveness of pavement
preservation activities, promote the use of frequent detailed
pavement condition surveys, and facilitate the establishment
of a dedicated budget for pavement maintenance. The need for
preventive pavement maintenance is well-recognized. About
56% of all respondents systematically identify pavements that
would benefit most from preventive maintenance and approximately 35% of respondents implement preventive maintenance
treatments at the right time. Approximately 33% of airport
agencies have a dedicated budget for pavement maintenance.
The main challenge facing airport authorities is not the
type of M&R treatment, but is to justify that M&R treatments
are necessary using a judicious and objective process, and to
obtain funding for their implementation.
Pavement management technology is mature. More than
80% of all airport authorities surveyed operate an Airport
Pavement Management System (APMS) or are in the process
of developing one. All airport agencies surveyed that have an
APMS use a pavement management software application, primarily MicroPAVER. It is expected that the new web-based
FAA pavement management software now under development, called AIRPAVE, will further enhance the technology
of the APMS.
Based on the survey, the average frequency of Pavement
Condition Index surveys was 3.3 years. Annual condition sur-
veys of pavement surface distresses on the candidate pavement
sections, such as sections with newly constructed and rehabilitated pavements aids in the selection and timing of preventive
pavement maintenance treatments.
There is no recognized single pavement roughness standard
for in-service airport pavements that could be used to identify
M&R needs based on pavement roughness. However, the
FAA has recently proposed roughness criteria for runways
addressing isolated bump events. Establishing practical roughness standards for the scheduling of M&R treatments on inservice airport pavements continues.
The performance of specific M&R treatments, particularly
treatments that are not routinely used, are typically tracked by
pavement managers. This enables the airport authority to
expand, modify, or discontinue M&R treatments based on
their documented field performance. Pavement management
software applications, such as MicroPaver or AIRPAVE, currently do or will include features to facilitate the evaluation of
past pavement M&R treatments.
About 35% of responding airports have recently (during
the past 10 years or so) evaluated the performance of new
and innovative M&R treatments. The data on the costeffectiveness of new and innovative treatments, as well as
the treatments that utilize proprietary products, are lacking.
Seventy percent of airports surveyed had both asphalt concrete (AC) and portland cement concrete (PCC) pavements on
at least some types of airport facilities, and 30% of airports had
both AC and PCC pavements on runways. Consequently,
many airports need to have staff that has expertise in the technology of both AC and PCC pavements. To present information in a concise structured way, 24 common M&R treatments
were systematically described in the Catalog of Airport Pavement Preservation Treatments in Appendix B.
The 50 airport survey sample size did not permit desegregation of results by geographical or environmental regions,
or by airport size.
Multi-year prioritization using incremental cost-effectiveness analysis, the most advanced method for optimizing
the allocation of available funding used by transportation
agencies administering large highway networks, is seldom
used for airport pavement networks. The reasons for slower
40
implementation include smaller airport pavement networks,
greater importance of operational issues at airports, and limitations of existing airport pavement management software.
Life-cycle cost analysis, a systematic assessment of other
treatment attributes important to an airport, can aid in the
selection of alternative M&R treatments. These attributes
may include, for example, agency experience with the performance of the alternatives, impact on airport operations,
and environmental and sustainability considerations.
A comprehensive review of an APMS could use gap
analysis that identifies differences between the existing management procedures and those based on the best appropriate
practice. The comparison between the results achieved by
different APMSs can be assessed through benchmarking.
Further research includes making pavement preservation
knowledge available to practitioners by organizing and synthesizing information and data in an interactive electronic
format.
41
GLOSSARY OF TERMS
This section contains the definitions of 26 key terms used in
the airport pavement management area. The objective of the
glossary of terms is to facilitate communication between all
concerned parties. It is not intended to override the established
usage of terms by various agencies. The terms are listed in an
alphabetical order.
Airport Pavement Maintenance Management Program—
The main characteristics of this program are defined by
Public Law 103-305 (2004). Briefly, the program specifies
how airport agencies should monitor and report the condition of airport pavements to be eligible for federal funding
for pavement preservation.
Airport Pavement Maintenance Management System—
Application of management principles to the maintenance of
airport pavements. The terms airport pavement maintenance
management system and airport pavement management
system are sometimes use interchangeably depending on the
understanding of what constitutes pavement maintenance.
Airport Pavement Management System (APMS)—A
pavement management system (defined subsequently)
applied to airfield pavements.
Asset management—A systematic process of maintaining,
upgrading, and operating physical assets cost-effectively.
Pavement maintenance is part of the management of airport
assets. It is typically assumed that an asset management
process can provide a logical approach to the management
of assets by combining engineering science with sound
business and accounting practices. The other desired feature
of asset management is that it can facilitate coordination of
planning and funding actions across all types of physical
assets, such as pavements, buildings, and guidance and
lighting installations.
Budgeting—A process of developing, securing, and administering a budget.
Corrective maintenance—Also called reactive maintenance, is defined as a maintenance activity performed after
pavement defects occur; that is, loss of pavement friction,
rutting, or cracking. Corrective maintenance treatments
are generally less desirable than preventive maintenance
treatments. However, preventive maintenance treatments,
such as crack sealing, also correct pavement defects. It is
also possible that a specific corrective maintenance treatment is the right treatment at the right time. Other differences between corrective and maintenance are discussed
under preventive maintenance.
Emergency maintenance—Maintenance treatments performed during an emergency situation, such as filling in a
large pothole or removing foreign object debris, for both
old and new pavements.
Life-cycle cost analysis—An economic analysis procedure
used to compare alternative pavement structures or pavement preservation strategies and treatments over an extended
period of time (often 20 years or more) taking into account
life-cycle costs. The life-cycle costs include agency costs
(initial construction costs and all subsequent maintenance
and rehabilitation costs), as well as user costs (such as the
cost of operational delays or restrictions during construction). The quantification of user costs in monetary terms is
not always used and is not always possible.
Multi-year planning—A process that plans future pavement
preservation activities on the network level over a period
of 5 years or more.
Network-level management—Management activities carried out at the network level concern all or a substantial
part of airport pavements. Decisions made at the network
level are typically planning, budgeting, or policy decisions.
Pavement condition—A measure of the way the pavement
serves the intended purpose. Pavement condition can be
described using the characteristics of individual defects
such as roughness or the lack of pavement friction, or using
characteristics that combine the influence of several defects
such as a Pavement Condition Index (PCI). Pavement condition assessment also includes pavement structural evaluation and testing.
Pavement maintenance—A strategy to maintain pavements
in the desired condition. Traditionally, for roadway pavements, pavement maintenance treatments are those that do
not substantially improve pavement condition or add to
pavement strength, such as crack and joint sealing. For
airport pavements, the term pavement maintenance often
encompasses both maintenance and rehabilitation treatments. The possible reason for using “maintenance” as a synonym for “maintenance and rehabilitation” is Public Law
103-305 (1994). This law requires that a public airport must
implement an “effective airport pavement maintenancemanagement program as a precondition for being considered for funding of replacement or reconstruction of airport
pavements.” This phraseology links a maintenance management program with replacement and reconstruction.
The Government Accounting Standards Board, which influences how expenses appear on financial statements, defines
maintenance as the act of keeping fixed assets in an acceptable condition; that is, keeping conditions at satisfactory
rather than at initial design levels (Lemer 2004). In this
report, the term pavement maintenance means the traditional definition of maintenance as a treatment that does not
substantially modify the existing pavement surface layers.
Pavement maintenance treatment—A specific maintenance action; a part of a pavement maintenance strategy.
Pavement management—A process that assists the custodians of pavement networks in finding optimum strategies
for providing and maintaining pavements in a serviceable
condition over a period of time.
Pavement Management System—An application of pavement management principles that encompasses a wide
42
spectrum of activities including periodic evaluation of
pavement condition, planning and programming of pavement preservation activities, pavement design, and construction. For airport pavements, a pavement management
system is also called an airport pavement maintenance system. Some airports may operate two complementary systems, one for airfield pavements and one for roads and
parking lots.
Pavement performance—Pavement condition recorded
over a period of time. Pavement performance describes
how the pavement condition changes over time.
Pavement preservation—Also known as airport pavement
preservation, this is a program of activities designed to
preserve the investment in the nation’s airport pavements.
Pavement preservation is a sum of all activities undertaken
to keep pavements in good repair and to meet the users’
needs. Pavement preservation includes routine maintenance,
emergency maintenance, preventive maintenance, corrective maintenance, and rehabilitation. Pavement preservation
treatments include treatments ranging from crack sealing
to asphalt overlays and a full-depth slab replacement. The
FHWA Pavement Preservation Expert Task Group defined
pavement preservation as “a program employing a network level, long-term strategy that enhances pavement
performance by using an integrated, cost-effective set of
practices that extend pavement life, improve safety and
meet motorist expectations” (Pavement Preservation
Compendium II 2006).
Pavement rehabilitation—A strategy undertaken to restore
pavement to its original condition using rehabilitation
treatments such as pavement overlays and the replacement
of failed portland cement concrete slabs.
Pavement rehabilitation treatment—Treatments undertaken to substantially improve the pavement condition.
The boundary between maintenance and rehabilitation
treatments is not well defined. A thin overlay may be considered to be either a maintenance or a rehabilitation treatment. The same treatment (such as a full-depth slab repair)
may be called a maintenance treatment, if only a very few
slabs are repaired, or a rehabilitation treatment, if multiple
slabs are repaired. Typically, rehabilitation treatments add
or replace one or more pavement surface layers. Some
agencies also distinguish between minor rehabilitation and
major rehabilitation. Pavements may receive several rehabilitation treatments (or undergo several rehabilitation
cycles) before they are reconstructed.
Planning—A process used to identify pavement preservation
needs. Planning includes elements of inventory, condition
evaluation, identification of needs, and prioritization.
Preventive maintenance—The definition of the preventive
maintenance has evolved. Originally, preventive maintenance was defined in 1997 by the AASHTO Standing
Committee on Highways as “. . . a planned strategy of
cost-effective treatments to an existing roadway system
and its appurtenances that preserves the system, retards
future deterioration, and maintains or improves the functional condition of the system (without significantly
increasing the structural capacity).” It typically includes
low-cost pavement treatments applied when the pavement
is in very good or good condition. Recently, preventive
maintenance has been defined in broader terms as a program of applying the right pavement preservation treatment to the right pavement at the right time. The preventive and corrective maintenance treatments are not defined
by the type of treatment, but by the reason why (or when)
the treatment is performed. For example, a microsurfacing
treatment applied to seal an open asphalt concrete pavement surface that starts to ravel can be considered a preventive maintenance treatment, whereas a microsurfacing
applied to an asphalt concrete pavement surface that is raveling (or to counteract moderate rutting) is a corrective
maintenance treatment. Consequently, the distinction
between preventive maintenance and corrective maintenance is blurred.
Programming—The process of developing implementation
plans (for pavement preservation) and acquiring the means
and resources necessary for implementation.
Project-level management—Activities at the project level
concern a specific pavement section. After deciding which
sections are selected to receive generic pavement preservation treatments at the network level, the project-level
decisions result in the selection of project-specific pavement preservation treatments, including the selection of
construction materials and procedures for implementation.
Project-level activities also include construction and subsequent monitoring of the treatment performance.
Routine maintenance—Also called operational maintenance,
this includes activities that do not substantially improve the
pavement surface, such as removal of debris representing
foreign object debris, snow and ice control, repainting of
pavement markings, maintenance of in-pavement runway
lights, and removal of rubber deposits. Routine maintenance
is not discussed in detail in the Synthesis.
Temporary maintenance treatment—Treatments designed
to hold the pavement surface together until more permanent or substantial rehabilitation takes place. Temporary
maintenance is also called holding maintenance or stopgap maintenance. Temporary maintenance treatments may
be necessitated by the timing of future rehabilitation or
reconstruction activities or by a lack of funds.
The right treatment to the right pavement at the right
time—The application of the right treatment to the right
pavement at the right time is the essence of a cost-effective
pavement preservation program. There is the ever-present
need to implement the right treatment at the right time. All
candidate pavement preservation treatments compete for
the same pavement preservation budget, with the “winner”
representing the best cost-effective method of providing
pavement infrastructure. The winner may be a single treatment or a combination of treatments.
43
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Broten, M., C. Comer, and A. Muntasir, “State Airport Pavement Management Practices and the Impact on Pavement
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Report FHWA-RD-00-166, Long Term Pavement Performance Program, Federal Highway Administration, Washington, D.C., 2000.
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SHRP-H-349, Transportation Research Board, National
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FAA Advisory Circular on Guidelines and Procedures for
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FAA Advisory Circular on Standardized Method of Reporting Airport Pavement Strength—PCN, AC 150/5335-5A,
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FAA Advisory Circular on Use of Nondestructive Testing
Devices in the Evaluation of Airport Pavements, AC
150/5370-11, Federal Aviation Administration, U.S.
Department of Transportation, Washington, D.C., 2004.
Federal Highway Administration, “Pavement Management
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http://fp2.org.
Geoffroy, D.N., Synthesis of Highway Practice 223: CostEffective Preventive Pavement Maintenance, Transportation Research Board, National Research Council, Washington, D.C., 1996, 103 pp.
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Discussion and Analysis for State and Local Governments,
Governmental Accounting Standards Board, Washington,
D.C., June 1999.
Haas, R., W.R. Hudson, and J. Zaniewski, Modern Pavement
Management, Krieger Publishing Company, Malabar,
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Hall, J.W., K.L. Smith, L. Titus-Glover, J.C. Wambold, T.J.
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Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements,
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Larkin, A. and G.F. Hayhoe, “Federal Aviation Administration Airport Pavement Management and Airport Pavement
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Lemer, A.C., NCHRP Synthesis of Highway Practice 330:
Public Benefits of Highway System Preservation and Maintenance, Transportation Research Board of the National
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Maintenance and Repair of Rigid Airfield Pavement Surfaces,
Joints, and Cracks, Engineering Technical Letter (ETL)
97-2 (Change 1), U.S. Department of the Air Force, U.S.
Department of Defense, Washington, D.C., Jan. 2004.
44
Michigan Airports Division, Michigan Airport Pavement
Management System, CD-ROM, Bureau of Aeronautics
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Michigan Department of Transportation, Capital Preventive
Maintenance Program Guidelines, Maintenance Division,
Michigan Department of Transportation, Lansing, 1999.
MicroPAVER, U.S. Army Construction Engineering Laboratory (USA-CERL), Engineering and Resources Development Centre, Champaign, Ill., 2003.
Minnesota Department of Transportation, Pavement Preventive Maintenance Program Guidelines, Office of Materials
and Road Research, Minnesota Department of Transportation, St. Paul, Jan. 8, 2001.
Ohio Department of Transportation, Pavement Preventive
Maintenance Program Guidelines, The Office of Pavement Engineering, Ohio Department of Transportation,
Columbus, 2001.
Pavement Engineering Assessment Standards, Engineering
Technical Letter (ETL) 04-9, U.S. Department of the Air
Force, Washington, D.C., Apr. 2004.
Pavement Maintenance Management, United Facilities Criteria UFC 3-270-08, U.S. Department of Defense, Washington, D.C., Jan. 2004.
Pavement Management Guide, AASHTO Joint Task Force
on Pavements, American Association of State Highway
and Transportation Officials, Washington, D.C., 2001.
Pavement Preservation Compendium II, Report FHWA-IF06-49, Federal Highway Administration, Washington,
D.C., 2006, 96 pp.
Pavement Preservation Toolbox, Federal Highway Administration, Washington, D.C., 2006 [Online]. Available:
www.pavementpreservation.org/toolbox/resources.html.
Peshkin, D.G., T.E. Hoerner, and K.A. Zimmerman,
NCHRP Report 523: Optimal Timing of Pavement Preventive Maintenance Treatment Applications, Transportation
Research Board of the National Academies, Washington,
D.C., 2004, 84 pp
Public Law 103-305, H.R. 2739, 108 Stat. 1569, Federal Aviation Administration Authorization Act of 1994 (enacted on
Aug. 23, 1994), Washington, D.C., 39 pp.
Shahin, M.Y., Pavement Management for Airports, Roads,
and Parking Lots, Chapman & Hall, London, 1994.
Shahin, M.Y., “Pavement Management–MicroPAVER
Update,” Proceedings of the 5th International Conference
on Managing Pavements, Seattle, Wash., 2001.
Smith, R.B., K. Russell, and J.M. Oakey, “A Methodology
for Measuring and Sustaining Best Appropriate Practice
in Road Management,” Proceedings of the 6th International Conference on Managing Pavements, Queensland,
Australia, Oct. 19–24, 2004.
Stroup-Gardiner, M. and S. Shatnawi, “The Economics of
Flexible Pavement Preservation,” CD-ROM, 88th Annual
Meeting of the Transportation Board, Washington, D.C.,
Jan. 11–15, 2009.
Tighe, S.L., M. Karim, A. Herring, K. Chee, and M.
Moughabghab, “Prioritization Methods for Effective Airport Pavement Management: A Canadian Case Study,”
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Tighe, S. and M. Covalt, Transportation Research Circular
E-C127: Implementation of an Airport Pavement Management System, Transportation Research Board of the
National Academies, Washington, D.C., 2008, 18 pp.
Transition Plan, AASHTO Pavement Preservation Lead
State Team, Washington, D.C., 2000 [Online]. Available:
http://leadstates.transportation.org/pp/transition/pp_tran
sition_plan.pdf.
Transportation Research Circular E-C012: Use of Artificial
Neural Networks in Geomechanical and Pavement Systems,
Transportation Research Board, National Research Council, Washington, D.C., Dec. 1999, 21 pp.
Unified Facilities Criteria on Pavement Maintenance Management, UFC 5-623, U.S. Department of Defense,
Washington, D.C., 2008.
Utah Continuous Airport System Plan 2007, Appendix A:
Airport Pavement Management System Review, Utah
Aeronautics, Utah Department of Transportation, Salt
Lake City, 2007.
Wade, M., D. Peshkin, K. Smith, and H.T. Yu, “Estimating
Remaining Life of Airfield Pavements,” Proceedings of
the 27th International Air Transportation Conference,
Advancing Airfield Pavements, American Society of Civil
Engineers, Reston, Va., 2007a.
Wade, M., A. Wolters, D. Peshkin, and M. Broten, “Prioritization of Airfield Rehabilitation Projects,” Proceedings
of the 27th International Air Transportation Conference,
Advancing Airfield Pavements, American Society of Civil
Engineers, Reston, Va., 2007b.
Walls, J. and M.R. Smith, Life-Cycle Cost Analysis in Pavement Design—Interim Technical Bulletin, Report FHWASA-98-079, Federal Highway Administration, Washington,
D.C., 1998.
Woods, J.E. and A.T. Papagiannakis, “Suitability of Runway
Pavement Roughness Indices in Capturing Aircraft
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Meeting of the Transportation Research Board, Washington, D.C., Jan. 11–15, 2009.
Zimmerman, K.A., “Sustaining the Use of Pavement Management Within an Organization,” Proceedings of the 6th
International Conference on Managing Pavements,
Queensland, Australia, Oct. 19–24, 2004.
Zimmerman, K.A. and A.S. Wolters, Pavement Preservation:
Integrating Pavement Preservation Practices and Pavement Management, Report FHWA-NHI-04-050, Federal
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Economic Concepts from an LCCA to a Pavement Management Analysis,” Paper No. 00-1351, 89th Annual Meeting of the Transportation Research Board, Washington,
D.C., Jan. 10–14, 2010.
45
APPENDIX A
Survey Questionnaire and Survey Responses
INTRODUCTION
The main source of information on current airport pavement maintenance practices was a survey of airport pavement maintenance professionals. The survey consisted of a four-page questionnaire which is reproduced herein in Tables 1A to 4A. The first two pages of the questionnaire
contain, in addition to the introductory material, 11 questions concerning airport pavement management practices. Tables 3A and 4A (pages 3
and 4 of the survey questionnaire) contain questions regarding the use and performance of common airport pavement maintenance and rehabilitation (M&R) treatments. Table 3A concerns M&R treatments applicable to asphalt concrete (AC) pavements, and Table 4A is for M&R treatments applicable to Portland cement concrete (PCC) pavements.
The objectives of the survey, the survey procedures, survey response rate, and the key results of the survey are described in the main part
of the synthesis. Additional survey results, that are not included in the main part of the report, are summarized in this appendix.
In order to present the survey results efficiently, Tables 3A and 4A also contain the entries that represent the number of survey responses
obtained. For example, referring to the first numerical entry in Table 3A, 37 airports reported routinely sealing cracks in AC pavements using
hot-poured sealant. The corresponding percentages are presented in Tables 3 and 4 of the main report. For example, according to Table 3,
95 percent of airports (that have AC pavements on at least some of the facilities) routinely seal cracks in AC pavements using hot poured sealant.
46
TABLE 1A
SURVEY QUESTIONNAIRE, PAGE 1 OF 4
Survey Questionnaire
Synthesis of Common Airport Pavement Maintenance Practices
This survey questionnaire is distributed to practitioners engaged in the maintenance and preservation of
airfield pavements. The results of the survey will be used to develop Synthesis of Common Airport
Pavement Maintenance Practices. The survey is sponsored by Airport Cooperative Research Program.
Details about the Program are available at http://www.trb.org/news/blurb_browse.asp?id=138.
Thank you for your participation in this survey. Please send the completed survey to Dr. Jim Hall by
email:
[email protected] or by fax: (601) 629-6169 before June 30, 2009. If you prefer to respond by a
telephone interview instead, please contact Dr. Jim Hall at (601) 629-6165
Respondent Information
Name: _________________________ Position: ______________________
Agency: _________________________ Address: _____________________________________________
Phone: ______________________ Fax: ___________________
Email:___________________________
General Facility Information
Facility Name or Code: ______________________________
What is the largest aircraft using your facility?
What is the predominant aircraft?
________________________________
________________________________
What pavement surface types do you have at your facility? (Please check all appropriate boxes)
Facility
Asphalt
Concrete (AC)
Portland Cement
Concrete (PCC)
Composite
(AC over PCC)
Surface
Treated
Gravel
Runways
Taxiways
Aprons
Pavement Management
1. Does your agency operate a pavement management system (or a pavement maintenance system)?
Yes
Under development
No
If yes, for how long has the system been in use?
3 to 5 years
5 to 10 years
More than 10 years
Less than 2 years
2. What is your experience with a pavement management system (or a pavement maintenance system)?
Please check all applicable boxes
Excellent, couldn’t do without it
The system is accepted and used
Not applicable
Benefits outweigh costs
Functional, but needs improvement
Not useful
3. Which pavement management (or pavement maintenance) software do you use or plan to adopt or
develop?
4. Who is involved in operating your pavement (or pavement maintenance) management system?
In-house staff
In-house staff with outside support
Mainly outside staff/consultant
47
TABLE 2A
SURVEY QUESTIONNAIRE, PAGE 2 OF 4
5. How do you use the results of pavement management (or pavement maintenance) system?
Please check all applicable boxes
To keep track of the pavement condition
To predict future pavement deterioration
To determine the performance of the past pavement maintenance and rehabilitation treatments
To prepare Capital Improvement Programs or annual budgets
To obtain funding from FAA or other agencies
6. How do you evaluate the condition of your pavements?
Pavement evaluation procedure
Pavement Condition Index (PCI)
Other types of surface distress surveys, but not PCI
If yes, what type of distress survey?
Pavement smoothness (or roughness) surveys
If yes, which roughness measure do you use?
Periodic pavement friction surveys
Periodic Falling Weight Deflectometer (FWD) surveys
Other surveys? Please specify (e.g., digital imaging of the
If yes, frequency of evaluation, years:
Runways
Other facilities
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
pavement surface)
7. How do you select pavement sections that require pavement maintenance or rehabilitation treatments?
Please check all applicable boxes
With the help of a computer program
Engineering judgement
Worst pavement condition first
Decision trees or guidelines
When a perceived hazard exist
Pavement age
Operational priorities
Other considerations
Preventive pavement maintenance is carried out to prevent premature pavement deterioration and is done
at the right time (when the treatment is most cost-effective). Preventive maintenance treatments may
include, for example, crack sealing or thin asphalt concrete overlays.
8. Do you systematically identify pavements that would benefit most from preventive maintenance?
When budget permits
No
Yes
9. Do you implement preventive maintenance treatment at the right time?
Yes
Sometimes
No
10. Has your agency recently (during last 10 years or so) evaluated the performance of specific pavement
maintenance or rehabilitation treatments? We are particularly interested in new and innovative
pavement preservation treatments and technologies.
Yes
No
If yes, please elaborate or tell us where we can get additional information._____________________
11. How do you obtain funding for pavement maintenance and rehab.? Please check all applicable boxes.
Through state funding
Through FAA funding
Have dedicated funding for preventive maintenance
Based on the last-year budget
Based on needs to preserve pavement
Based on pavement needs such as PCI level
48
TABLE 3A
SURVEY QUESTIONNAIRE, PAGE 3 OF 4
Maintenance and Rehabilitation of Asphalt Concrete Pavements
Which of the following maintenance treatments do you use, or have tried, during the past 10 years?
What is your experience in using them?
Maintenance of Asphalt Concrete Pavements
Performance
V. Good
Good
Poor
Hot- poured
37
5
8
30
4
Cold-applied
4
3
1
4
1
Hot mix
23
7
11 15
Cold mix
Proprietary
mix
19
8
3
12
9
4
5
2
4
2
Spray patching
(Includes manual chip seal)
2
3
Machine patching with AC
12
6
7
10
Milling and machine patching
15
8
7
11
Surface treatment
11
8
1
13
3
2
1
4
7
5
2
Treatment
Crack
sealing with
sealant
Small area
(pothole)
patching
using:
Texturization
Fine milling
Shot blasting
Unknown
Have Tried
Comments, questions, experience
Routine
Never Tried
Current
Practice
Please comment on your experience
with specific treatments
Do you recommend routing of cracks
No
before sealing? Yes
Sometimes
Do you recommend the use of proprietary
No
materials? Yes
5
1
2
Surry seal
10 11
2
15
3
Micro-Surfacing
1
4
1
3
Hot mix overlay
20 10
12
12
Milling and overlay
20
8
14 10
Hot in-place recycling
2
1
1
Cold in-place recycling
1
Whitetopping (PCC overlay)
3
3
3
1
1
Rejuvenators, fog seals, etc.
Other techniques/materials
that you are using?
(Please add)
13 10
5
13
4
1
1
1
Do you use hot mix overlays less than 1½”
thick?
Yes
No
49
TABLE 4A
SURVEY QUESTIONNAIRE, PAGE 3 OF 4
Maintenance and Rehabilitation of Portland Cement Concrete Pavements
Which of the following maintenance treatments do you use, or have tried, during the past 10 years?
What is your experience in using them?
Have Tried
V. Good
Good
Poor
12
6
2
12
1
Silicone sealant
16
9
5
12
Neoprene seal
3
9
4
4
Load
transfer
restoration
Sub-sealing
1
2
1
2
Slab stitching
1
2
1
2
Dowel retrofit
5
2
3
2
Shallow
patch repair
using
PCC
14
6
5
12
1
AC
12
8
3
11
3
Proprietary mix
7
7
5
5
2
PCC
19
6
8
8
1
8
16
4
7
2
3
7
3
5
2
1
1
1
1
2
14
3
11
Full and
partial depth AC
repairs or
replacement Proprietary mix
using
Precast panels
Diamond grinding
(under slab grouting)
6
4
1
Micro-surfacing
2
1
1
1
2
5
2
3
AC overlay
4
11
4
7
PCC overlay (white topping)
Other techniques/materials?
(Please add)
3
3
2
2
Please comment on your experience
with specific treatments
3
Controlled shot blasting
Machine patching with AC
Unknown
Routine
Bitumino us
sealant
Treatment
Joint/Crack
sealing
Never Tried
Maintenance of Exposed PCC Pavements
Current
Performance
Practice
Comments, questions, experience
Do you recommend the use of proprietary
No
materials? Yes
Do you recommend the use of proprietary
No
materials? Yes
1
Thank you for completing the survey. Please send the completed survey to Dr. Jim Hall by email:
[email protected] or by fax: (601) 629-6169 before June 30, 2009.
Applied Research Associates Inc. 112 Monument Place, Suite A, Vicksburg, Mississippi 39180-5156
50
ADDITIONAL SURVEY RESULTS
The key survey results are presented and discussed in the main part of the synthesis and are not reproduced herein. The following contains
additional survey results.
The survey questions are in an italic font; survey response data are in regular font.
What pavement surface type do you have at your facility?
Facility
Asphalt Concrete (AC)
Portland Cement Concrete (PCC)
Composite (AC over PCC)
Surface Treated
Gravel
Runways
37
23
13
3
1
Taxiways
37
24
8
1
0
Aprons
30
32
7
1
0
See Figure 11 in the main part of the synthesis. Figure 11 is based on 30 responses.
1. Does your agency operate a pavement management system (or a pavement maintenance system)?
Yes
Under development
No
No.
29
11
8
Percent
60
23
17
If yes, for how long has the system been in use?
See Figure 4, which is based on 28 responses.
2. What is your experience with a pavement management system (or a pavement maintenance system)?
See Figure 5. Figure 5 is based on 33 responses of agencies that operate an airport pavement management system. None of the respondents
checked “not useful.”
3. Which pavement management (or pavement maintenance) software do you use or plan to adopt or develop?
See Figure 22, which is based on 33 responses. An additional 17 respondents checked “not applicable.”
4. Who is involved in operating your pavement (or pavement maintenance) management system?
See Figure 23, which is based on 39 responses.
5. How do you use the results of pavement management (or pavement maintenance) system?
See Figure 6, which is based on 38 responses.
6. How do you evaluate the condition of your pavements?
See Table 2, which is based on 38 responses.
7. How do you select pavement sections that require pavement maintenance or rehabilitation treatments?
See Figure 14, which is based on 47 responses.
8. Do you systematically identify pavements that would benefit most from preventive maintenance?
See Figure 15, which is based on 48 responses
9. Do you implement preventive maintenance treatment at the right time?
See Figure 17, which is based on 30 responses.
10. Has your agency recently (during last 10 years or so) evaluated the performance of specific pavement maintenance or rehabilitation
treatments?
Yes
No
No response
Number
17
27
3
Percent
36
58
6
See section “Survey Results” in chapter four for the list of innovative and additional treatments.
51
11. How do you obtain funding for pavement maintenance and rehabilitation?
See Figures 19 and 20, each based on 48 responses. Regarding the dedicated funding for preventive maintenance, see Figure 15.
Additional information regarding maintenance and rehabilitation treatments of asphalt concrete pavements.
Do you recommend routing of cracks in AC pavements before sealing?
Yes
No
Sometimes
No response
Number
15
2
20
23
Percent
34
4
23
39
Do you recommend the use of proprietary materials for small area patching of AC pavements?
Yes
No
Sometimes
No response
Number
14
9
10
17
Percent
32
20
23
25
Additional information regarding maintenance and rehabilitation treatments of portland cement concrete pavements.
Do you recommend the use of proprietary materials for shallow patch repairs?
Yes
No
No response
Number
3
10
16
Percent
5
12
83
Do you recommend the use of proprietary materials for full depth repairs?
Yes
No
No response
Number
4
4
33
Percent
10
10
80
RESPONDING AIRPORTS
Table 5A lists all 50 airports and airport agencies that completed the survey questionnaire. Also listed in Table 5A are the airport location,
the average number of daily aircraft operations, and pavement type of airfield pavements. Geographical location of the airports is illustrated
in Figure 1 of the main report.
52
TABLE 5A
LIST OF AIRPORTS
State
Airport Name
Location
Arkansas
Ozark Regional Airport
Mountain Home
California
Eight small airports, the
largest is Gillespie Field
County of San
Diego
Meadows Field Airport
Bakersfield
Colorado Springs
Municipal Airport
Sussex County Airport
St. Augustine/St. Johns
County Airport
LaGrange Callaway
Airport
Savannah/Hilton Head
International Airport
Hartsfield–Jackson Atlanta
Int. Airport
Chicago O’Hare
International Airport
Chicago Midway
International Airport
Dubuque Regional Airport
Des Moines International
Airport
Hammond Northshore
Regional Airport
Houma–Terrebonne
Airport
Baltimore Washington
International Airport
Easton Airport
Boston Logan
International Airport
Detroit Metro. Wayne
County Air.
Gulfport–Biloxi
International Airport
Hesler–Noble Field
Springfield–Branson
Regional Airport
Saint Paul Downtown
Airport
Minneapolis–St. Paul
International Airport
Dawson Community
Airport
Great Falls International
Airport
Omaha Epply Airfield
Colorado
Springs
Georgetown
Colorado
Delaware
Florida
Georgia
Illinois
Iowa
Louisiana
Maryland
Massachusetts
Michigan
Mississippi
Missouri
Minnesota
Montana
Nebraska
New Jersey
New Mexico
New York
Ohio
Average
No. of Daily
Operations
136
Pavement
Type
AC
1 to 669
AC
344
Both
420
Both
57
Both
St. Augustine
347
AC
LaGrange
47
AC
Savannah
267
Both
Atlanta
2,939
PCC
Chicago
2,563
Both
Chicago
730
Both
Dubuque
155
Both
Des Moines
333
Both
Hammond
210
Both
Houma
243
Both
Baltimore
760
Both
Easton
137
AC
Boston
1,094
Both
Romulus
1,266
Both
Gulfport
153
Both
Laurel
63
Both
Springfield
181
Both
St. Paul
435
AC
St. Paul
1,240
PCC
Glendive
16
AC
Great Falls
115
Both
Omaha
366
Both
Essex County Airport
Morristown Municipal
Airport
Albuquerque International
Airport
Dona Ana County
Airport
Caldwell
245
AC
Morristown
403
AC
Albuquerque
522
AC
Santa Teresa
89
AC
JFK International Airport
Queens
1,291
Both
Port Columbus
International Airport
Columbus
449
Both
77
Both
Vandalia
300
Both
Altus
38
PCC
Mansfield Lahm Airport
Dayton International
Airport
Altus/Quartz Mountain
Reg. Air.
53
TABLE 5A
(continued)
State
Oklahoma
Oregon
Pennsylvania
Texas
Utah
Virginia
Washington
Washington
DC
Wyoming
N/A = not available.
Airport Name
Arrowhead Airport
Boise City Municipal
Airport
Portland International
Airport
28 airports throughout
Oregon
Wilkes–Barre/
Scranton Int. Air.
Lone Star Executive
Airport
Mineral Wells Airport
George Bush
Intercontinental Air.
Salt Lake City
International Airport
Washington Dulles
International Airport
Winchester Regional
Airport
Seattle Tacoma
International Airport
Snohomish County Airport
Ronald Regan National
Airport
Airports throughout
Wyoming
Average
No. of Daily
Operations
Pavement
Type
Canadian
1
AC
Boise City
10
AC
Portland
630
Both
Oregon
N/A
Both
Avoca
178
Both
Conroe
219
Both
Mineral Wells
62
AC
Houston
1,577
Both
Salt Lake City
1,071
Both
Chantilly
1,048
PCC
Winchester
100
Both
Seatac
946
PCC
Everett
Washington,
D.C.
311
Both
754
PCC
N/A
Both
Location
Wyoming
54
APPENDIX B
Catalog of Airport Pavement Preservation Treatments
CONTENTS
Introduction
55
AC AND PCC PAVEMENTS
FACT SHEET 1—TEXTURIZATION USING SHOT BLASTING
58
FACT SHEET 2—DIAMOND GRINDING
60
FACT SHEET 3—MICROSURFACING
57
AC PAVEMENTS
FACT SHEET 4—SEALING AND FILLING CRACKS IN AC PAVEMENT
62
64
FACT SHEET 5—SMALL AREA PATCHING
FACT SHEET 6—SPRAY PATCHING (MANUAL CHIP SEAL AND MECHANIZED SPRAY PATCHING)
FACT SHEET 7—MACHINE PATCHING OF AC PAVEMENT USING BITUMINOUS MATERIALS
70
FACT SHEET 8—RESTORATIVE SEALS
72
FACT SHEET 9—TEXTURIZATION USING FINE MILLING
74
FACT SHEET 10—SURFACE TREATMENT (CHIP SEAL, CHIP SEAL COAT)
76
FACT SHEET 11—SLURRY SEAL
78
FACT SHEET 12—HOT-MIX OVERLAY OF AC PAVEMENT
80
FACT SHEET 13—HOT IN-PLACE RECYCLING OF AC PAVEMENT
82
FACT SHEET 14—COLD IN-PLACE RECYCLING OF AC PAVEMENT
84
FACT SHEET 15—ULTRA-THIN WHITETOPPING OF AC PAVEMENT
PCC PAVEMENTS
FACT SHEET 16—JOINT/CRACK SEALING OF PCC PAVEMENT
86
88
FACT SHEET 17—PARTIAL-DEPTH (PATCH) REPAIRS OF PCC PAVEMENT
90
FACT SHEET 18—FULL-DEPTH (PATCH) REPAIRS OF PCC PAVEMENTS
FACT SHEET 19—MACHINE PATCHING OF PCC PAVEMENT WITH AC MATERIAL
94
FACT SHEET 20—SLAB STABILIZATION AND SLABJACKING
96
FACT SHEET 21—LOAD TRANSFER RESTORATION
98
FACT SHEET 22—CRACK AND JOINT STITCHING
100
FACT SHEET 23—AC OVERLAYS OF PCC PAVEMENTS
102
FACT SHEET 24—BONDED PCC OVERLAY OF PCC PAVEMENTS
92
66
68
55
INTRODUCTION
The objective of the Catalog of Airport Pavement Preservation Treatments is to describe common airport pavement preservation
treatments for both asphalt concrete (AC) and portland cement concrete (PCC) airfield pavements, and to include materials, methods,
and applications. The information is organized in the form of Fact Sheets. Each pavement preservation treatment is described on a
separate Fact Sheet using a set format.
Selection of Treatments Included in the Catalog
This appendix includes 24 Fact Sheets, each describing pavement preservation treatments as listed in Table B1. These 24 treatments
were compiled from responses to the questionnaire sent to airport managers and engineers that identified 38 separate treatments as
part of this synthesis project. Additional information was obtained from the 35 referenced documents listed in the Resource sections
of this appendix. The survey is described in chapter one, the survey questionnaire in Appendix A, the key survey results are described
throughout the report, and additional survey results are summarized in Appendix A.
Briefly, 50 survey responses were obtained from a geographically diverse set of airports ranging in size from one to approximately
3,000 daily aircraft operations. Thirty-eight pavement preservation treatments were included on the survey form for respondents to
review; these encompassed commonly used pavement preservation treatments for AC and PCC pavements. The 24 treatments
included in the catalog were taken from the 50 responses and each of these has been used routinely by at least one of the airports surveyed, or they have been tried by at least 10% of the airports. All treatments included in the survey satisfied these inclusion criteria
with the exception of microsurfacing used for PCC pavements.
The 38 treatments included in the survey were reduced to 24 treatments included in the catalog by combining treatments that
differed primarily by the material used or by the pavement type to which the treatment is applied. An example of combining treatments that differ only by the material used is the combination of two types of crack sealing of AC pavements (using hot-poured
sealant or using cold-applied sealant) into one treatment (sealing and filling of cracks of AC pavement). An example of combining treatments that differ primarily by the pavement type is microsurfacing of AC pavements and microsurfacing of PCC pavements, which became one treatment—microsurfacing. As a result, the Catalog includes 3 pavement preservation treatments
applicable to both AC and PCC pavements, 12 treatments applicable to AC pavements, and 9 treatments applicable to PCC pavements (see Table B1).
TABLE B1
AIRPORT PAVEMENT PRESERVATION TREATMENTS INCLUDED IN THE CATALOG
Both Pavement Types
3 treatments
Asphalt Concrete
12 treatments
Portland Cement Concrete
9 treatments
16) Joint and crack sealing (with
bituminous, silicone, or
compression sealants)
1) Texturization using shot
blasting
4) Sealing and filling of cracks (with
hot or cold applied sealants)
2) Diamond grinding
5) Small area patching (using hot
mix, cold mix, or proprietary
material)
17) Partial depth repairs (using AC,
PCC, and proprietary materials
6) Spray patching (manual chip seal
and mechanized spray patching)
18) Full-depth repairs (using AC,
PCC, and proprietary materials
7) Machine patching with AC
material
19) Machine patching using hot
mix
8) Rejuvenators and seals
20) Slab stabilization and slabjacking
3) Microsurfacing
9) Texturization using fine milling
21) Load transfer
10) Surface treatment (chip seal, chip
seal coat)
22) Crack and joint stitching
11) Slurry seal
23) Hot-mix overlays
12) Hot-mix overlay (includes milling 24) Bonded PCC overlay
of AC pavements)
13) Hot in-place recycling
14) Cold in-place recycling
15) Ultra-thin whitetopping
56
Sources of Information
Information sources used for the preparation of the catalog were similar to those used for the report and are described in the Methodology section in chapter one of the synthesis report. In addition, each Fact Sheet contains a section titled “Resources,” which typically contains two or three source references and additional information. The main purpose of these references is to direct the reader
to key publications containing general and specific information on the treatment. The number of references listed on the Fact Sheets
was restricted for brevity.
References used in development of the fact sheets included:
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division, Lansing,
Apr. 2010.
Ohio Department of Transportation, Pavement Preventive Maintenance Guidelines, Office of Pavement Engineering, Columbus,
May 2001.
Minnesota Department of Transportation, Preventive Maintenance Best Management Practices of Hot Mix Asphalt Pavements,
Report MN/RC-2009-18, Office of Materials and Road Research, Maplewood, May 2009.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Wu, Z., J.L. Groeger, A.L. Simpson, and G.R. Hicks, Performance Evaluation of Various Rehabilitation and Preservation Treatments, Office of Asset Management, Federal Highway Administration, Washington, D.C., Jan. 2010.
Organization of the Catalog
The Catalog consists of 24 Fact Sheets, each describing a separate pavement preservation treatment. Although the pavement preservation treatments are described separately, several treatments can be used on the same pavement section at the same time, or at different times, as part of a single pavement rehabilitation project or strategy. For example, a single PCC pavement rehabilitation project may include four maintenance and rehabilitation (M&R) treatments: shallow patch repair, full-depth repair, diamond grinding,
and joint/crack resealing.
The order in which the M&R treatments are described in the Catalog was set up according to the following rules:
1. Treatments that can be applied to both AC and PCC pavements without any substantial modification are described first, followed
by the description of treatments applicable to AC pavements and PCC pavements.
2. For each pavement type, the treatments are arranged in an approximate order of their increasing contribution to restoring pavement serviceability.
The Fact Sheets describe treatments using a uniform format. Each Fact Sheet starts with a sketch showing a sequence of operations,
and a short definition of the treatment.
Service lives and unit costs of the pavement preservation treatments given in the Fact Sheets provide relative information that can be
used for orientation and comparison purposes only. The service lives and costs are based on a literature review and apply to typical
situations only. The synthesis survey included questions on the usage and performance of pavement preservation treatments, but not
on their life spans and costs.
57
Fact Sheet 1—Texturization Using Shot Blasting
Debris storage
Abrasive storage
Blast wheel
Vacuum
separator
Schematic of Shot Blasting Operation
Shot blasting is a texturization technique that uses a self-propelled machine that blasts abrasive particles onto the pavement surface
as shown in the above schematic. The objective is to remove contaminants, such as rubber deposits and excess asphalt cement (AC),
and to abrade deteriorated surface material to restore both micro- and macrotexture. Surface retexturing with shot blasting can be used
for both AC and PCC (portland cement concrete) pavements to improve pavement friction.
Sources of Information and Additional Resources
The source document and additional general information is from Gransberg, “Life-Cycle Cost Analysis of Surface Retexturing with
Shotblasting as an Asphalt Pavement Preservation Tool,” Transportation Research Record: Journal of the Transportation Research
Board, No. 2108, Transportation Research Board of the National Academies, Washington, D.C., 2009, pp. 46–52.
Purpose and Selection Criteria
Unlike fine milling and diamond grinding, shot blasting does not improve pavement smoothness. It can be used to improve pavement
friction by removing materials from the pavement surface, to clean pavement surface before the application of sealants, and to remove
traffic control lines and signs. The best improvement in pavement surface friction by shot blasting is achieved when abrasion-resisting
aggregate particles are embedded in a mortar that can be abraded by shot blasting.
Typical Service Life and Costs
When used to restore pavement friction by removing softer or deteriorated material, the treatment effectiveness may last 1 to 6 years.
When used to remove rubber deposits on runways, the effectiveness depends on the formation of new rubber deposits. The cost is typically lower than for diamond grinding and is in the range of approximately $2 to $10 per square yd.
Materials and Construction
There are several types of proprietary equipment that can produce a pattern width ranging from approximately 6 in. to 6 ft. The equipment includes a system that propels abrasive particles, such as small round steel pellets, onto the pavement surface, vacuums up the
resulting pavement material debris and abrasive particles, separates the abrasive particles from debris for re-use, and stores the debris
for disposal. The technique is commonly applied to PCC pavements, but has also been successfully used on both AC and surfacetreated surfaces.
Airport Experience
Just over 20% of airports surveyed reported that they have tried using shot blasting for PCC or for AC pavements. None of the airports reported routine use of shot blasting for either pavement type. Typically, the performance of shot blasting was reported as good.
58
Fact Sheet 2—Diamond Grinding
Schematic of Diamond Grinding Operation
Diamond grinding is a rehabilitation technique that removes a shallow depth of pavement surface material by saw cutting closely spaced
grooves into the pavement surface using diamond-tipped blades. The above illustration shows a self-propelled diamond grinding
machine.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division,
Lansing, Apr. 2010.
Ohio Department of Transportation, Pavement Preventive Maintenance Guidelines, Office of Pavement Engineering, Columbus,
May 2001.
Additional resources include a comprehensive manual of practice; the Concrete Pavement Repair Manual was issued by American Concrete Pavement Association (ACPA) in 2003 and is available from www.pavement.com.
American Concrete Pavement Association, Diamond Grinding and Concrete Pavement Restoration, Report TB008P, Skokie, Ill., 2000.
Purpose and Selection Criteria
The purpose of diamond grinding is to improve pavement smoothness and/or improve pavement surface friction. When used to
improve pavement smoothness, diamond grinding is applied only to selected areas of the pavement. For example, to remove slab stepping (faulting), grinding can be applied to selected transverse joints. When used to improve pavement surface friction, diamond grinding is typically used over the entire pavement area.
Diamond grinding can remove up to 3⁄4 in. from the pavement surface and can remove surface defects and irregularities such as
polished or scaling surface and faulting, and improve pavement surface smoothness. When used to correct faulting, the faulting is
expected to be relatively stable in terms of progression and typically does not exceed approximately 1⁄4 in. Diamond grinding is often
used as the penultimate treatment in a PCC rehabilitation project, done after load transfer restoration, and partial and full-depth
repairs. The last treatment is for joint and crack resealing.
Diamond grinding will not address the underlying cause of pavement structural problems and is inappropriate for surfaces with
material problems such as durability (D)-cracking or alkali-reactive aggregate.
Typical Service Life and Costs
The restoration of pavement surface friction by diamond grinding may last 5 to 12 years. Grinding to improve pavement smoothness
on faulted slabs may last only a few years, particularly if the original faulting was progressing and the underlying reasons for the faulting were not addressed.
Typical cost of diamond grinding is in the range of $4 to $12 per square yard, depending on quantities and the hardness of the
aggregate.
Materials and Construction
Diamond grinding employs a large drum, equipped with closely spaced diamond-tipped teeth, mounted on a moving heavy-set framework. The best results are achieved with continuous operation employing wide grinding drums. When several grinding passes are
required to cover one traffic lane, the passes typically overlap by less than 2 in. The diamond grinding operation is carried out in the
longitudinal direction, and preferably against the predominant direction of aircraft operations.
The spacing between the diamond-tipped saw blades is such that the ridges (or fins) left between the blades break readily, approximately 2 or 3 mm, depending on the strength of the concrete (Figure B1). If the ridges do not break off readily, the spacing between
the blades can be reduced. Diamond grinding results in a characteristic corduroy texture with high pavement surface friction produced
by the combination of smoothly cut channels and rough surface where the ridges have broken off.
59
Land area:
1/10 inch typical for hard aggregate
1/8 inch typical for soft aggregate
Width of saw cut
(1/10 to 1/7 inch)
Depth of saw cut
(1/17 to 1/13 inch)
FIGURE B1 Profile of diamond-grooved
surface. Improved pavement surface friction is
provided by the land area created by the brokenoff ridges.
Slurry resulting from the grinding operation (water is used to cool diamond-tipped blades and suppress dust) is continuously vacuumed and collected. Diamond grinding done only to improve pavement surface friction on relatively new pavements may not require
resealing of joints. Grinding done to correct faulting on older pavements is typically followed up by joint resealing.
Airport Use
About 8% of airports surveyed use diamond grinding routinely, and approximately 46% of airports surveyed have tried using it. All
airports that routinely use or have tried using diamond grinding rated its performance as very good or good.
60
Fact Sheet 3—Microsurfacing
Portland cement
Aggregate
Emulsion
Pug mill
Optional
tack coat application
Spreader box
Water spray
Application unit
Feeder & propulsion unit
Asphalt distributor
Schematic of Microsurfacing Operation
Microsurfacing is an unheated mixture of polymer-modified asphalt emulsion, high-quality frictional aggregate, mineral filler, water,
and other additives, mixed and spread over the pavement surface as a slurry. The construction of microsurfacing using a self-propelled
truck-mounted continuous-feed mixing machine is illustrated by the schematic above.
The aggregate skeleton used for microsurfacing consists of high-quality interlocking crushed aggregate particles. Consequently,
it is possible to place microsurfacing in layers thicker than the largest aggregate size, or in multiple layers, without the risk of permanent deformation.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division,
Lansing, Apr. 2010.
Ohio Department of Transportation, Pavement Preventive Maintenance Guidelines, Office of Pavement Engineering, Columbus,
May 2001.
Minnesota Department of Transportation, Preventive Maintenance Best Management Practices of Hot Mix Asphalt Pavements,
Report MN/RC–2009-18, Office of Materials and Road Research, Maplewood, May 2009.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
The International Slurry Surfacing Association (ISSA) maintains a website at www.slurry.org, which contains recommended specifications
and useful guidance for microsurfacing (Recommended Performance Guidelines for Micro-Surfacing, A143).
Purpose and Selection Criteria
Microsurfacing is used to correct surficial distresses such as slight block cracking, raveling and segregation, flushing, and loss of
pavement friction. Because microsurfacing contains high-quality crushed aggregate it is also used to fill in ruts and surface deformation to the depth of up to 13⁄4 in. Microsurfacing can also be used to extend the service life of the pavement until a more permanent
restoration can be completed.
As a preventive maintenance treatment it can be used to seal the surface of the pavement, protecting the pavement from water infiltration and greatly reducing the rate at which the existing AC surface oxidizes. Microsurfacing is also used on PCC pavements to
improve or maintain frictional resistance and smoothness.
Typical Service Life and Costs
When used to protect the existing pavement structure as a preventive maintenance treatment, microsurfacing can prolong pavement
life span by 4 to 6 years. When used to restore or improve pavement surface; for example, to restore pavement friction or to repair
wheel track rutting, microsurfacing can last 5 to 8 years.
The cost of one application of microsurfacing is approximately $3 to $6 per square yard, typically approximately 75% of the cost
of a single hot-mix overlay.
Materials and Construction
Microsurfacing mix is always designed by a contractor or an emulsion supplier. Figure B2 shows a finished product a year after construction. The ISSA recommends two types of gradations, Type II and Type III. The Type II gradation is finer, with 90% to 100%
61
FIGURE B2 Microsurfacing
texture one year after
construction; diameter of
the coin is 1 in.
passing a 4.75 mm sieve. The Type III gradation is coarser with 70% to 90% of aggregate passing the No. 4 sieve size, and can be
used on runways. A minimum thickness of microsurfacing mix using Type III gradation is 0.4 in. for a single course.
The surface on which microsurfacing is applied is expected to have uniform pavement condition. Areas that exhibit significantly
more severe defects than the remainder of the section (e.g., raveling, cracking, or rutting) are repaired. The repairs can by made using
an additional course of microsurfacing or by other means depending on the type, extent, and severity of the defects. On high traffic
volume facilities, and/or when the surface of the pavement has minor distortions and/or has ruts exceeding approximately 1⁄4 in., two
courses of microsurfacing are used. The first (scratch) course is intended to improve the profile of the pavement and the second course
provides the wearing surface. Ruts exceeding 1⁄2 in. are typically filled with microsurfacing material using a rut-filling spreader box.
After the microsurfacing application, traffic can use the pavement without restrictions in about 45 to 120 minutes, depending on
setting time of the asphalt emulsion, weather, and traffic conditions. Microsurfacing is typically carried out only during the warmer,
dryer months. Cooler temperatures and wetter conditions can result in longer curing times during which the microsurfacing can be
damaged by traffic.
Airport Experience
Microsurfacing can be used for both AC and PCC pavements. For AC pavements, only one airport surveyed used microsurfacing routinely, and two airports surveyed have tried using it. For PCC pavements, only one of the surveyed airports indicated use of microsurfacing.
62
Fact Sheet 4—Sealing and Filling Cracks in AC Pavement
Locate
Rout
Clean
Seal
Illustration of Crack Routing, Cleaning, and Sealing
Crack sealing is a maintenance technique that cleans cracks and seals them with a rubberized bituminous compound. The crack sealing typically includes routing of the crack to create a reservoir for the sealant at the top of the crack, as shown in the illustration above.
Crack sealing without routing is called crack filling. Crack filling is not as cost-effective as crack sealing and is easily damaged by
snow plows. For this reason, this Fact Sheet concentrates only on crack sealing.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division,
Lansing, April 2010.
Ohio Department of Transportation, Pavement Preventive Maintenance Guidelines, Office of Pavement Engineering, Columbus,
May 2001.
Minnesota Department of Transportation, Preventive Maintenance Best Management Practices of Hot Mix Asphalt Pavements,
Report MN/RC–2009-18, Office of Materials and Road Research, Maplewood, May 2009.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
Michigan Department of Transportation produced a manual, Sealing and Filling of Cracks for Bituminous Concrete Pavements,
Selection and Installation Procedures, which is available on CD and distributed by Foundation for Pavement Preservation, Austin,
Tex. [Online]. Available: www.fp2.org.
A useful summary of information is available from Crack Seal Application, Pavement Preservation Checklist Series, Publication
FHWA-IF-02-005, produced by the Foundation for Pavement Preservation, Austin, Tex. [Online]. Available: www.fp2.org.
UFC 3-250-08FA, Standard Practice for Sealing Joints and Cracks in Rigid and Flexible Pavements.
Purpose and Selection Criteria
The purpose of crack sealing is to prevent water from entering the pavement structure and damaging it. Crack sealing is most effective in a wet-freeze environment. It is applied to “working or active” cracks. These cracks change in width during the year because
of temperature changes, and include both transverse cracks and longitudinal cracks. Figure B3 shows how water from melting snow
enters the pavement through unsealed cracks. Infiltrated water, together with the effect of freeze–thaw cycles and pavement loads,
FIGURE B3 Water from melting snow readily enters pavement
structure through a transverse crack.
63
FIGURE B4 Transverse crack heaving caused by water that
saturated pavement structure and froze.
leads to heaving of the cracks (Figure B4) and to the deterioration of the pavement structure beneath the crack. The additional benefit of sealing is the prevention of spalling and raveling of unsealed crack edges.
Crack sealing is typically done soon after transverse and longitudinal cracks develop, often when the pavement is 2 to 5 years old.
At that time, the crack pattern would be well-developed and the crack would reach the width of 0.1 to 0.4 in. at moderate temperatures. The initial crack sealing is typically followed by a second sealing carried out when new cracks appear or when the original
sealant no longer works, often after another 3 to 5 years.
Crack sealing is most cost-effective for thick AC pavements. It is typically not cost-effective for thin AC pavements with the total
thickness of the AC layer less than 3 in. Thin pavements tend to develop many secondary cracks that cannot be effectively sealed or
filled.
Typical Service Life and Costs
The expected life of crack sealing is about 2 to 7 years. The crack sealing performance depends on the crack and pavement condition,
sealant material, rout configuration, and construction procedures. Typical cost of rout-and-seal treatment is approximately $2 to $3
per linear yard.
Materials and Construction
There are many AC sealants on the market and their performance can differ significantly. Hot-poured rubberized bituminous sealants are
most often used. Some agencies are not satisfied with the existing specifications for sealants (e.g., ASTM D6690 or AASHTO T187-60)
and have modified them.
The reservoir for the sealant at the top of the crack is created by a router. The opinions regarding the size and shape of the most
effective reservoir differ. It is generally agreed that routs with greater width than depth and a rectangular shape are preferable. The
routed crack is typically cleaned before sealing.
The sealant is heated in a double-jacketed kettle to avoid exposure of the sealant to direct heat. It is important to avoid overheating or re-heating the sealant, and dispersing the sealant into the crack by a device (a pump wand) that maintains the sealant at a desired
temperature. Because the sealant shrinks after the installation and cooling, the hot sealant is installed “proud” of the surface.
Until the sealant hardens and there is no danger that it will be picked up by passing tires, it is covered by a bond-breaking material
such as sawdust or flour. The use of cement or mineral dust is typically avoided. Occasionally, it is necessary to seal cracks wider than
30 mm. These cracks can be temporarily repaired by fine aggregate hot mix or liquefied patching materials similar to a slurry material.
Airport Use
Based on the survey, a majority of all airports routinely perform crack sealing using a hot-poured bituminous sealant. The majority
of the airports surveyed reported good performance of crack sealing. Only a small minority of airports surveyed use cold-applied
sealants routinely. The majority of airports surveyed rout cracks prior to sealing.
64
Fact Sheet 5—Small-Area Patching
Select
Clean
and trim
Apply a
tack coat
Add
patching
material
Compact
The Sequence of Operations for Small Patching Repairs
Small-area patching is a maintenance treatment that includes placing and spreading of bituminous mixtures, hot or cold, to repair potholes and other pavement distresses without the use of mechanical pavers or graders. The illustration shows the sequence of operations. The patching with hot mix or cold mix can be used for both bituminous pavements and PCC pavements; however, permanent
repairs of PCC pavements are typically done using PCC material. If pavers or graders are used, the treatment is called machine patching and is described on a separate Fact Sheet.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Additional resources include:
A useful manual of practice was issued by the Federal Highway Administration as Report FHWA-RD-99-168, Materials and Procedures for Repair of Potholes in Asphalt-Surfaced Pavements: Manual of Practice, and is available at www.tfhc.gov/pavement/
ltpp/pdf/99168.pdf.
Several highway agencies have developed manuals for patching of AC pavements. One of the most comprehensive has been published by the Minnesota Technology Transfer Center, Best Practices Handbook on Asphalt Pavement Maintenance, Manual
No. 2000-04, Minneapolis, 2000.
Purpose and Selection Criteria
Small-area patching is used to repair localized defects such as potholes, distortion resulting from utility cuts, and small areas with severe
ravelling and/or alligator cracking. The repair of potholes such as the one shown in Figure B5 reduces pavement roughness and the rate
of pavement deterioration by improving drainage and reducing dynamic traffic loads. The repairs may be permanent, semi-permanent,
or temporary.
Permanent repairs—Permanent repairs are used on pavements that are in good condition to bring the life span of the repaired area
in line with that of the rest of the pavement. Permanent repairs require the use of appropriate patching materials and techniques,
with the goal of addressing the underlying cause of the defects being repaired. Unless the original cause for the pavement
defects is corrected, the repairs are susceptible to early failure.
Semi-permanent repairs—Semi-permanent repairs have a typical life expectancy of one or two years. Usually, the area is not saw
cut and may be repaired with cold mix.
Temporary repair—Temporary repairs are used to hold the pavement until it can be resurfaced or permanently repaired. They are
also used as emergency repairs when the pavement condition may pose a hazard to airplane operations.
FIGURE B5 Untreated pothole collects water and accelerates
pavement deterioration.
65
Typical Service Life and Costs
Temporary patching repairs may last one year or less; permanent repairs may last 10 years or more. The cost of small-area patching
is highly dependent on the extent of the repairs and on the selection of patching material. A typical unit cost for small-area patching
is $20 to $40 per square yard.
Materials and Construction
The main types of patching materials include hot mix, local or agency-specified cold mix, and proprietary cold mix. A tack coat, if
used, is typically an emulsion diluted with additional water. Hot-mix AC patching material provides the most durable treatment. Some
suppliers of proprietary cold patching mixes suggest that their products can achieve similar performance and that their products can
be successfully applied to potholes containing water. Cold mixes with single-size aggregate may not perform well in relatively large
repairs. The single-size aggregate mix has low stability and is susceptible to rutting and ravelling.
Typically, small-area permanent patching repair includes the following steps:
•
•
•
•
Removal of broken pavement material in the patch area by jack hammering, cold milling, and/or pavement sawing.
Cleaning out loose material from the patch area by blowing or brushing.
Applying a tack coat to provide a bond between the existing pavement and the patching material.
Placing the bituminous mix into the patch area. If the patch area is deeper than 2 in., the mix is placed and compacted in lifts
until the level of the surrounding pavement is reached.
• Compacting the mix with a steel or rubber-tire roller, a vibratory plate compactor, or a hand tamper. Depending on the size and
depth of the repair, and the material used, the finished repair will have crown of 0.1 to 0.4 in.
• Sealing the joint between the patch and the original pavement with hot-poured crack sealant. Sealing is typically done for larger
and deeper repair areas.
Airport Experience
Patching is one of the most common pavement maintenance treatments. According to survey respondents, the majority of airports
(that have AC pavements) routinely use small-area patching using hot mix and a minority of airports routinely use cold mix. None of
the agencies surveyed reported poor performance of repairs using hot mix, whereas approximately 20% of agencies surveyed reported
poor results using cold mix. A small minority of agencies surveyed routinely used a proprietary mix.
66
Fact Sheet 6—Spray Patching (Manual Chip Seal and Mechanized Spray Patching)
Power broom
or sweeper
Rubber-tired
roller
Self-propelled
aggregate spreader
Asphalt emulsion
distributor
Schematic of Chip Seal Operation
Spray patching is a maintenance treatment that includes the application of bituminous material followed by spreading of cover aggregate. The technological sequence is shown in the above schematic. Spray patching can be done manually or by specialized self-propelled
equipment that sprays an emulsion, applies the cover aggregate, and provides the initial compaction—all in one pass. Mechanized spray
patching applied on the full-width of a facility, such as a taxiway, and that is longer than 100 ft, is called surface treatment. The Catalog
contains a separate Fact Sheet for surface treatments.
Sources of Information and Additional Resources
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Asphalt Recycling and Reclaiming Association, Basic Asphalt Recycling Manual, Annapolis, Md., 2001.
Additional information includes:
U.S. Department of Transportation, Pavement Preservation Compendium II, Publication FHWA-IF-06-049, Sep. 2006.
InfraGuide 2005: Preservation of Bituminous Pavement Using Thin Surface Restoration Techniques, 2005 [Online]. Available:
http://gmf.fcm.ca/Infraguide/Roads_and_Sidewalks.asp.
Purpose and Selection Criteria
Spray patching is used to slow down pavement deterioration of vulnerable localized areas or to repair localized pavement distresses
such as ravelling, flushing, and block cracking. A properly applied spray patching produces an all-weather surface that seals the pavement surface, prevents or retards propagation of surficial distresses, and can provide improved surface friction. The use of spray
patching to repair or slow down the progression of transverse or longitudinal cracks is not considered to be cost-effective.
Manual spray patching is suitable for localized repairs. Machine patching is typically used to repair large areas that do not require
full-width coverage.
Typical Service Life and Costs
The typical life span of spray patching is 2 to 5 years. A typical cost of spray patching is in the range of $3 to $8 per square yard,
depending primarily on the quantity of work.
Materials and Construction
Manual spray patching employs a variety of bituminous products (applied hot or cold) and aggregates (chips, graded aggregate, or
sand). Typically, bituminous products used for spray patching are emulsions heated to less than 185°F.
Aggregate used for mechanized spray patching is typically open-graded (chips). Aggregate used for manual patching can be dense
or open-graded with a typical maximum aggregate size of approximately 1⁄2 in. Sand is also used.
Manual application of emulsion is done with a hand wand or a spray bar. Cover aggregate is applied immediately after spraying
emulsion. Compaction with truck tires or rubber-tired rollers follows. Generally, after compaction, 75% of the height of the aggregate particles is imbedded in the emulsion.
The procedure for manual spray patching typically consists of the following steps:
• Removal of all loose material and debris.
• Spraying of an emulsion in a uniform manner.
• Application of aggregate to obtain even coverage.
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• Compaction; wheels of the truck used to supply the cover aggregate can be used for compaction.
• Sweeping off loose aggregate around and over the patch.
Spray patching is generally carried out only during the warmer, dryer months. Cooler temperatures and wetter conditions prolong setting (hardening) of the emulsion and the time the repairs are susceptible to damage by traffic.
Airport Experience
Spray patching used to be one of the key maintenance treatments for AC pavements. However, the usage of manual spray patching
has been declining. Only a few airports surveyed routinely use spray patching or have tried it.
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Fact Sheet 7—Machine Patching of AC Pavement Using Bituminous Materials
1. Rubber tired rollers
2. Static dual steel drum rollers
Hot mix truck
Asphalt distributor
Paver
Optional built-in tack coat application
Optional tack coat
Schematic of Machine Patching Operation
Machine patching of AC pavements is a maintenance technique that involves placing and spreading of premixed bituminous materials (hot or cold mix) using a mechanical paver or a grader on parts of a pavement section. As shown in the illustration, machine patching includes the application of tack coat, placement of the patching material, and compaction.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division of Maintenance, Sacramento, 2008.
Additional resources includes:
SHRP H 348: Asphalt Pavement Repair Manuals of Practice, Materials, and Procedures for the Repair of Potholes in AsphaltSurfaced Pavements, Strategic Highway Research Program, Transportation Research Board, National Research Council,
Washington, D.C., 1993.
Purpose and Selection Criteria
Typical applications of machine patching include repairs of localized areas of ravelling and segregation, alligator cracking, potholing, rutting, frost heaving, and subgrade settlement. The areas selected for patching are expected to be well-defined and separated by
areas that are in good condition. If the areas requiring patching are closely spaced, it may be more cost-effective to resurface the entire
section.
Machine patching repairs can be divided into permanent and semi-permanent repairs:
Permanent repairs—Permanent patching repairs can be used on pavements that are in good condition to bring the life span of the
repaired area in line with that of the rest of the pavement. For example, if it is expected that the pavement being repaired will
require resurfacing in 8 years, the patching repair could be done to also last approximately 8 years.
Semi-permanent repairs—Semi-permanent repairs have a limited life expectancy and are used typically when it is anticipated that
the entire pavement will be resurfaced within a few years. To save costs, the extent of patching is limited and the patched area
may not receive a tack coat.
Typical Service Life and Costs
Permanent repairs may last 5 to 12 years or more; semi-permanent repairs may last approximately 5 years or less. A typical cost of
machine patching is $10 to $25 per square yard.
Materials and Construction
For permanent repairs, the same type of hot mix may be used for patching as that used for the surface of the existing asphalt pavement. Typically, permanent machine patching includes the following steps:
• Structural repairs—If the patch is over an area exhibiting structural weakness (e.g., alligator cracking, rutting, or depression
and settlement) it may be necessary to remove some or all of the underlying base and subbase material. The granular base is
restored and re-compacted. The additional pavement strength, if required, is achieved by replacing some part of the granular
material with AC to avoid increasing the overall thickness of the pavement structure.
• Removal of the deteriorated AC layer by milling—Milling may be required to maintain pavement elevation or to provide a
smooth transition between the original pavement and the patch. Figure B6 shows a construction detail for the start of a long
patch.
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Wedge milling
1¼ inch minimum
2 to 4 feet
Finished overlay
FIGURE B6 Wedge milling to key in a
11⁄4-in.-thick AC patch.
• Application of a tack coat at the sides of the patch and over the entire patched area to improve the bond between the original
pavement and the patch, and to minimize water infiltration.
• Placing of the mix. The placement is done by a paver. The material is placed in layers not exceeding 3 in. The minimum thickness of a permanent machine-placed patch is typically 11⁄4 in.
• Compaction of the patch area using rollers.
• Application of a sealant at the joint of the patch and the existing pavement. Resealing the joint if it opens in a few years.
Airport Experience
About one-half of all survey respondents routinely use or have tried using machine patching. A large majority of respondents reported
very good or good performance.
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Fact Sheet 8—Restorative Seals
Emulsion distributor
Optional
light sanding
Schematic of Restorative Sealing Operation
Restorative seals consist of an application of a bituminous or coal-tar material, typically emulsion-based, to the surface of AC pavement as illustrated by the schematic. Restorative seals are also called rejuvenators or fog seals. Some agencies or suppliers recommend light sanding of fog seals (approximately 1 lb of sand per square yard).
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division of Maintenance, Sacramento, 2008.
Minnesota Department of Transportation, Preventive Maintenance Best Management Practices of Hot Mix Asphalt Pavements,
Report MN/RC-2009-18, Office of Materials and Road Research, Maplewood, May 2009.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
Shoenberger, J.E., “Skid Resistance of Rejuvenated Airfield Pavements,” Proceedings of the 27th International Air Transportation
Conference, Advancing Airfield Pavements, American Society of Civil Engineers, Reston, Va., 2007.
Engineering Technical Letter 03-8, Rejuvenation of Hot-Mix Asphalt (HMA) Pavements, Dec. 2003.
Boyer, R. and D.I. Hanson, Non-Coal-Tar Fuel Resistant Sealers and HMA Systems: State-of-the-Practice, prepared for Airfield
Asphalt Technology Program Project 05-02, May 2008.
Purpose and Selection Criteria
Restorative seals can serve one or more of following three purposes:
To seal the surface—Restorative seals can reduce penetration of water by sealing small cracks and porous pavement surfaces.
Restorative seals can slow the progression of raveling and coarse aggregate loss, and have been used shortly after paving to
seal areas with low to moderate segregation. The sealing can also slow down oxidation and hardening of AC.
To rejuvenate oxidized and hardened asphalt binder—Restorative seals used primarily to revitalize the surface of the AC pavement are called rejuvenators. Rejuvenators are intended to penetrate the surface of the AC pavement and reverse the oxidation
and hardening process in the AC. The depth of penetration is usually only 0.1 to 0.2 in. Rejuvenators do not leave much residual material on the surface and can be re-applied.
To provide protection against fuel spills and oil leak—Aircraft fuels and lubricants are chemically compatible with AC, can dissolve it, and degrade the surface of AC pavements. Restorative seals that are not compatible with AC can provide protection
from the damaging effects of fuel spills and oil leaks.
Typical Service Life and Costs
A restorative seal is a temporary fix generally lasting 1 to 3 years. The cost can range from $0.5 to $2 per square yard.
Materials and Constructions
Restorative seals designed to seal the pavement surface use slow or medium setting asphalt emulsion further diluted with water.
Aggregate, if applied to provide better pavement friction, is typically medium to fine sand with the particle size of less than 0.05 in.
Restorative seals designed to function as rejuvenators or as rejuvenators/sealers contain proprietary materials that may contain solvents. Restorative seals for the protection against fuel spills and oil leaks are typically coal-tar sealers—an emulsion of coal tar stabilized with clay. Acrylic-modified bituminous emulsions can also increase protection against fuel spills.
Restorative seals are sprayed on the pavement surface by distributors. Asphalt emulsion is typically heated to about 175°F
before the application to pavement that is in good condition and has been broomed before the restorative seals are applied. With
71
correct application rates, and in some instances the use of sand, restorative seals can generally provide satisfactory levels of pavement friction.
Airport Experience
About one-half of the airports surveyed routinely use or have used restorative seals, and a large majority of the users reported very
good or good performance.
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Fact Sheet 9—Texturization Using Fine Milling
Power
broom
Conventional
Precision
Micro
Self-propelled milling unit
Cutting Teeth Spacing
0.6 to 0.8 inches
0.2 to 0.5 inches
0.2 inches
Schematic of Milling Operation
Texturization techniques using milling include conventional milling, precision milling, and fine milling. Milling is done by a cylindrical milling drum with closely spaced carbide-tipped tools (teeth). The techniques differ by the spacing of the cutting teeth, as
shown on the above illustration, and by the degree of control over the profile of the milled surface. Fine milling, also called
micromilling, removes unevenness from the pavement surface or improves its texture, and leaves an abraded surface that can be used
as a driving surface.
Sources of Information and Additional Resources
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
The Basic Asphalt Recycling Manual by the Asphalt Recycling and Reclaiming Association provides guidelines for milling and other
texturization techniques.
Hall, K.L., J.W. Smith, and P. Littleton, NCHRP Report 634: Texturing of Concrete Pavements, Final Report, Nov. 2008, Transportation Research Board of the National Academies, Washington, D.C., Nov. 2008, 97 pp.
Purpose and Selection Criteria
Fine milling can improve pavement smoothness and pavement friction. Smoothness is improved by milling of protruding pavement
features such as bumps, stepping (faulting) at transverse cracks, and rutting. If the pavement has sufficient structural capacity, the
reduction in thickness is not of concern.
Figure B7 shows an example of pavement surface where micromilling was used to reduce rutting and roughness.
FIGURE B7 The milled surface has grooves with the peak-topeak distance of approximately 0.6 in.
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Typical Service Life and Costs
The expected service life of texturization using fine milling is 1 to 7 years. A typical cost is approximately $4 to $12 per square yard.
Materials and Construction
Milling is a general term used to describe the removal of the surface of AC or PCC materials from pavements by a self-propelled unit
having a cutting drum equipped with closely spaced carbide-tipped tools. Micromilling and precision-milling are types of milling that
strive to provide a more even platform for an overlay and/or a finished pavement surface. Micromilling and precision-milling operations are also called fine milling. The following definitions of micromilling and precision milling are not universally accepted and
are provided for orientation purposes only.
Micromilling—Typically, the depth of micromilling is up to 0.6 in. and results in a surface texture depth of about 0.04 in. with the
groove-to-groove spacing of 0.2 in. Such surface does not need an overlay.
Precision milling—Typically, the depth of precision milling is up to 1 in. and results in a surface texture depth of approximately
0.2 in. A precision-milled surface is usually overlaid.
Airport Use
A small minority of airports surveyed routinely use or have used fine milling. In addition, one responding airport reported using transverse grooving of the AC surface to improve pavement friction.
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Fact Sheet 10—Surface Treatment (Chip Seal, Chip Seal Coat)
Power broom
or sweeper
Rubber-tired Cover aggregate
rollers
Self-propelled
aggregate spreader
Asphalt
distributor
May be one unit
Schematic of Surface Treatment Construction Process
Surface treatment (also known as surface seal, seal, and chip seal) is the application of asphalt binder, immediately followed by an
application of cover aggregate, to any type of pavement surface. A typical construction process is shown in the schematic. If the
aggregate is of uniform size, the treatment is usually called chip seal. Typically, surface treatments are applied on top of a granular
base producing surface-treated pavement. Surface treatments can be also applied to AC pavements as a preventive or corrective maintenance treatment.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division,
Lansing, Apr. 2010.
Ohio Department of Transportation, Pavement Preventive Maintenance Guidelines, Office of Pavement Engineering, Columbus,
May 2001.
Minnesota Department of Transportation, Preventive Maintenance Best Management Practices of Hot Mix Asphalt Pavements,
Report MN/RC-2009-18, Office of Materials and Road Research, Maplewood, May 2009.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
Several agencies have published guidelines for the design and construction of surface treatments including the Minnesota Department
of Transportation (Janish, D.W. and F.S. Gaillard, Minnesota Seal Coat Handbook, Office of Research Services, St. Paul, 1998).
A recent NCHRP Synthesis of Highway Practice provides practical guidelines for the construction of surface treatments (Gransberg,
D. and D.M.B. James, NCHRP Synthesis of Highway Practice 342: Chip Seal Best Practices, Transportation Research Board of
the National Academies, Washington, D.C., 2005).
Purpose and Selection Criteria
Surface treatments applied on top of AC pavements can be used as preventive or corrective treatments. As a preventive measure, surface treatment is primarily used to seal the surface showing non-traffic-load associated cracks and ravelling. As a corrective measure,
surface treatment is used to restore frictional resistance and to maintain wearing surface on AC pavements. Surface treatments using
polymer-modified emulsions have been used as crack relief layers between the existing AC surface and an AC overlay, or as stress
relief layers between the existing PCC surface and an overlay.
Typical Service Life and Costs
When used to protect the existing pavement structure as a preventive maintenance treatment, surface treatment can prolong pavement
life span by 4 to 6 years. When used to restore or improve pavement surface; for example, to restore pavement friction, surface treatment can last 5 to 8 years. The cost of a single surface treatment is approximately $2 to $4 per square yard.
Materials and Construction
The surface on which surface treatment is applied is expected to have a uniform capacity to absorb emulsion. Active cracks, such as
transverse and longitudinal cracks, can be sealed prior to application of the surface treatment.
Typically, the asphalt binder used for surface treatment is asphalt emulsion applied at an elevated temperature (120°F to 180°F)
using an asphalt distributor. The cover aggregate can be either chips (open-graded aggregate) or dense-graded as shown in Figure B8.
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FIGURE B8 Surface of a newly constructed surface treatment using 5/8-in.-dense-graded aggregate and
high-float emulsion.
About 70% of the aggregate is typically imbedded or surrounded by the binder. The need for accurate application of the binder and
aggregate cover is facilitated by modern asphalt distributors, which can automatically maintain selected application rates regardless of
the distributor speed. Newly constructed surface treatments need to be protected from traffic for several hours after construction.
Emulsion application rates for seal coats typically range from 0.2 to 0.4 gallon per square yard depending on the existing surface
(granular, seal coat, or AC) and aircraft operations, and are further adjusted during construction according to weather conditions and
other factors.
Airport Use
A small number of the surveyed airports indicated routine use of surface treatments, or have tried them. However, the majority of
responding airports that routinely use or have used surface treatment rated its performance as good. Some of the reasons reported for
low usage of surface treatments by airports are probably concerns about loose aggregate, dust, and rougher surface texture.
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Fact Sheet 11—Slurry Seal
Portland cement
Aggregate
Pug mill
Spreader box
Emulsion
Water spray
Schematic of Slurry Seal Construction
Slurry seal is an unheated mixture of asphalt emulsion, graded fine aggregate, mineral filler, water, and other additives, mixed and
uniformly spread over the pavement surface as slurry. The construction of slurry seal using a self-propelled truck-mounted mixing
machine is illustrated by the above schematic. Slurry seal systems are formulated with the objective of creating a bitumen-rich mortar. They are similar to microsurfacing, but the mineral skeleton is typically not very strong and has limited interlocking of the aggregate particles. Consequently, slurry seals are applied in thin lifts to avoid permanent deformation by traffic.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
No. FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
The ISSA maintains a website, www.slurry.org, that contains recommended specifications for slurry seal [International Slurry Surfacing Association, Recommended Performance Guidelines for Microsurfacing, Document ISSA A143 (revised), 2005].
Engineering Brief No. 35A, SEP 27 1994, Thermoplastic Coal-Tar Emulsion Slurry Seal, Amended Interim Specification, Federal
Aviation Administration, Washington, D.C.
Purpose and Selection Criteria
Slurry seals are used to correct surficial distresses such as raveling and coarse aggregate loss, seal slight cracking, and improve pavement friction. They are also used as a preventive maintenance treatment to seal pavement surfaces from intrusion of water and slow
surface oxidation and ravelling. Slurry seals are best placed on structurally sound pavements that are in good condition with little or
no cracking or rutting.
Slurry seals perform best on surfaces with uniform characteristics. If defects such as moderate or severe ravelling, cracking, or
rutting occur frequently, the section is probably not a good candidate for slurry sealing. Working cracks, such as transverse cracks,
can be sealed either before or after the slurry seal application.
Typical Service Life and Costs
When used as a preventive maintenance treatment, slurry seal can prolong pavement life span by 3 to 6 years. When used to restore
or improve pavement surface characteristics, for example to restore pavement friction, slurry seals can last 3 to 7 years. The cost of
slurry seal is approximately $2 to $4 per square yard, typically less than half of the cost of a hot-mix overlay.
Materials and Construction
Asphalt emulsion used in slurry seals is typically cationic and contains about 60% to 65% of residual AC. The slurry mix contains
9% to 10% of AC. Coal tar-based emulsions that provide protection against fuel spills and oil leaks are also available in some
markets.
Aggregate used for slurry seals is crushed high-quality dense-graded aggregate. Its gradation generally follows one of the three
gradation types, Type I, II, or III, recommended by the ISSA. Type II gradation can be used for aprons and low-volume taxiways and
Type III gradation for runways. Type III gradation has 70% to 90% of aggregate passing No. 4 sieve.
Mineral filler, typically portland cement or hydrated lime, is used to control curing time of the mix (break time of the emulsion).
The amount of mineral filler is typically less than 1% of the total dry mix weight. The thickness of a slurry seal application is slightly
more than the thickness of the largest aggregate particle in the mix, typically approximately 0.4 in.
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Some proprietary slurry seal mixes contain crushed aggregate particles and polymer-modified emulsion and may have strength
and durability characteristics that are closer to a microsurfacing than to a traditional slurry seal.
The slurry seal mixture is supplied using a specialized equipment that carries all of the components of the mixture, accurately measures and mixes them in a pug mill, and spreads the mixture (by means of a spreader box linked to the mixing unit) in a strip 10 to 12 ft
wide as a thin, homogeneous coat of slurry mix.
Slurry seals are typically carried out only during the warmer, dryer months. After the slurry seal application, traffic can use the
pavement without restrictions (except 360 degree turns by aircraft) in approximately 45 to 120 min, depending on setting time of the
asphalt emulsion, weather condition, and traffic conditions. Cooler temperatures and wetter conditions can result in long curing times
during which the slurry seal can be damaged by traffic.
Airport Experience
A small number of surveyed airports reported the use of slurry seals routinely, or have tried using them. The majority of responding
airports that use slurry seals reported very good or good performance.
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Fact Sheet 12—Hot-mix Overlay of AC Pavement
1. Optional vibratory dual steel drum rollers
2. Rubber tired rollers
Optional material
3. Static dual steel drum rollers
transfer vehicle
Paver
Optional built-in tack coat application
Hot mix truck
Asphalt distributor
Power
broom
Milling
machine
Tack coat application
Schematic of Hot-Mix Overlay Construction Process
Hot-mix overlay of AC pavement consists of placing a layer or layers of hot mix over the existing AC surface. The above illustration
shows the construction of an overlay including milling of the pavement surface, application of a tack coat, and the use of a material
transfer vehicle.
Conventional AC overlays are usually constructed with a minimum thickness of 11⁄2 in. Overlays that are less than 11⁄2 in. thick are
called thin overlays and typically require special construction provisions.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division,
Lansing, Apr. 2010.
Ohio Department of Transportation, Pavement Preventive Maintenance Guidelines, Office of Pavement Engineering, May 2001.
Minnesota Department of Transportation, Preventive Maintenance Best Management Practices of Hot Mix Asphalt Pavements,
Report MN/RC-2009-18, Office of Materials and Road Research, Maplewood, May 2009.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
No. FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Another useful manual on the construction of asphalt overlays is from the Asphalt Institute (Asphalt Overlays for Highway and Street
Rehabilitation, Manual Series No. 17, Lexington, Ky., 1998).
Purpose and Selection Criteria
Overlays are used to restore pavement serviceability by improving ride quality and providing a new waterproof surface that covers cracking, ravelling, rutting, polished pavement surface, and other pavement defects. Overlays are also used as a preventive maintenance treatment to seal pavement surfaces from intrusion of water, slow surface ravelling, seal small cracks, and improve surface friction.
Overlays can be used to strengthen the pavement structure to accommodate increased pavement loads. In this case, overlay thickness is determined by appropriate pavement design procedures.
Single overlays are typically constructed over structurally sound pavements. Areas that exhibit weakness (e.g., settlement, alligator cracking, and rutting) can be strengthened by patching or even by full-depth repairs. Some agencies rout and seal cracks in the
existing AC pavement before placing an overlay, and carry out full-depth repairs of deteriorated transverse cracks.
Typical Service Life and Costs
Hot-mix overlays have an expected service life of 7 to 12 years depending on overlay thickness, traffic loads, existing pavement condition, environment, and material and construction quality. A typical cost of constructing an AC overlay is in the range of $60 to $90
per ton of material placed. For a 2-in.-thick single overlay, the corresponding cost is approximately $6 to $9 per square yard.
Materials and Construction
There are many variations in the material of hot mix. Some of the common variations are outlined in the following.
Dense-graded and open-graded mixes—The two main types of hot mix used for overlays are dense-graded and open-graded
mixes. Dense-graded mixes have aggregate particles that are fairly uniformly distributed. Open-graded mixes contain a large
percentage of one-size coarse aggregate resulting in a mix with interconnected voids and high permeability. Open-graded
mixes provide good pavement friction and reduce the potential for hydroplaning (Figure B9).
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FIGURE B9 (Left) Thin open-graded hot-mix overlay surface;
(Right) Dense-graded overlay surface. Diameter of the coins
is 0.7 in.
Virgin or recycled mixes—The use of recycled material in hot mix is common, particularly for a binder course. For surface courses
on runways, the use of virgin materials is usually specified.
Superpave—Introduced in 1992 to the highway industry, the Superpave system represented a new system for designing AC mixes.
The Superpave system includes the use of performance-graded asphalt binder specifications and Superpave mix design procedures.
Fuel resistant mixes—There are currently two proprietary hot mixes on the U.S. market that are designed to resist degradation
caused by aircraft fuel spills and leaks of lubricants and hydraulic oils. In general, lower air voids and stiffer AC increase the
fuel resistance of the mix.
The existence of distresses such as ravelling, segregation, and cracking may dictate partial-depth removal (cold milling) of the AC
prior to resurfacing. Partial-depth removal is normally accomplished using cold milling equipment. Grade-controlled precision
milling may also be used to restore longitudinal and cross-sectional pavement profile and to improve smoothness of the subsequent
overlay. The reclaimed asphalt pavement material may be reused as hot or cold mix or mixed with granular material. A tack coat is
typically used before placing an overlay. A tack coat is a typically slow or medium setting asphalt emulsion diluted with water.
Airport Experience
A majority of surveyed airports routinely use or have tried using hot-mix overlays with or without prior milling, and nearly all surveyed airports reported very good or good performance. No responding airports reported using thin overlay (with thickness of less
than 11⁄2 in.).
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Fact Sheet 13—Hot In-Place Recycling of AC Pavement
1. Vibratory dual steel drum rollers
2. Rubber-tired rollers
3. Static dual steel drum rollers
Re-former
Hot mix for
integral overly
Infrared
heaters
Second screed
Leveling and profiling
Mixing
Adding rejuvenator
Scarifying
Optional addition of aggregate
and/or beneficiating hot mix
Schematic of Hot In-Place Recycling Process
Hot in-place recycling (HIR) is a pavement rehabilitation method that involves reprocessing of the existing AC material in-place at
temperatures normally associated with hot-mix AC paving. The illustration above shows the construction of HIR with an integral
overlay using a reformer.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division of Maintenance, Sacramento, 2008.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
The 1997 FHWA publication Pavement Recycling Guidelines for State and Local Governments (Report FHWA-SA-98-042, National
Technical Information Service, Springfield, Va.) describes all aspects of recycling of asphalt pavement materials to produce new
pavement materials.
Button, J.W., D.N. Little, and C.K. Estakhri, Synthesis of Highway Practice 193: Hot In-Place Recycling of Asphalt Concrete, Transportation Research Board, National Research Council, Washington, D.C., 1994.
Taylor, M. and E. Dillman, “Airport Saves with Hot-in-place Recycling,” Public Works, Vol. 19, No. 10, 1999.
Purpose and Selection Criteria
HIR is suitable for structurally sound pavements with surface defects, such as raveling and segregation, cracking, and rutting that
affect mainly the top pavement surface layer. An additional requirement is that the AC surface layer is suitable for recycling, has a
uniform composition (aggregate gradation, asphalt content, and thickness), and materials of good quality (aggregate and asphalt
binder). Material properties of pavements considered for HIR are thoroughly evaluated. Because of the size of a recycling train, HIR
is suitable for large projects with room to maneuver.
Typical Service Life and Costs
The success of HIR depends on the properties of the existing materials, quality and quantity of new materials added, quality of construction, and the thickness and type of the surface layer placed on top of the HIR mix. Consequently, the expected service life can
range from about 5 to 12 years. Overall, HIR pavements can perform comparably to conventional asphalt surfaces.
A typical cost of a hot-in-place recycling layer is in the range of $5 to $10 per square yard.
Materials and Construction
There are other types of HIR processes and equipment in addition to the process illustrated above. Typical HIR construction consists
of the following steps:
• Heating of the existing AC surface—Several methods are available including infrared heating panels, flame burners, and
microwave heating.
• Pavement scarification—The depth of scarification is usually limited (by the capacity of the heaters) to the top 21⁄4 in. of the
AC surface.
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• Adding new materials and mixing—Depending on the properties of the existing AC material, the added new materials may
include a combination of rejuvenating agents and (hot) aggregate, or the addition of a beneficiating hot mix. The objective is to
compensate for deficiencies in the asphalt material to be recycled.
• Levelling and reprofiling of the recycled mix—Some improvement can be made to the pavement profile. Addition of new AC
overlay is necessary to make significant corrections to profile.
• Placement of a thin hot-mix layer (optional)—Some HIR recycling equipment can add new hot-mix material on top of the recycled mix as an integral overlay. The thickness of the integral overlay is typically 11⁄4 in. The total thickness of the recycled and
new mix is typically up to 3 in.
• Compaction—Standard compaction procedures utilizing vibratory steel drum rollers, rubber tired rollers, and static steel drum
rollers are employed.
The resulting recycled layer can be used as a wearing surface or can be protected by a slurry seal, surface treatment, or a hot-mix overlay. If an integral overlay is used, the overlay serves as the wearing surface.
HIR is typically carried out only during the warmer, dryer months. Cooler temperatures and wetter conditions can result in longer
heating times leading to the overheating and burning of the pavement surface, and creating smoke and vapors. Cooler ambient temperatures can also result in lower mix temperatures leading to an insufficient depth of scarification, fracturing aggregate during scarification, and poor compaction of the mix.
Airport Experience
None of the airports surveyed used hot-in-place recycling. However, hot-in-place recycling has been used for the rehabilitation of
runways.
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Fact Sheet 14—Cold In-Place Recycling of AC Pavement
1. Rubber tired rollers
2. Static dual steel drum rollers
Mixing unit
Paver
Milling
machine
Schematic of Cold Recycling Process
Cold in-place recycling (CIR) is a pavement rehabilitation method that involves reprocessing of an existing hot-mix asphalt pavement at ambient temperatures, either in-place or in an off-site processing plant, and laying it back down. The illustration above shows
the construction of CIR. The recycled AC layer is typically covered by a hot-mix overlay.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
The 1997 FHWA publication Pavement Recycling Guidelines for State and Local Governments (Report FHWA-SA-98-042, National
Technical Information Service, Springfield, Va.) describes all aspects of recycling of asphalt pavement materials.
The FHWA also maintains a web page on “Cold In-place Recycling State of Practice Review” at: http://www.fhwa.dot.gov/Pavement/
recycling/cir/.
Purpose and Selection Criteria
CIR is a suitable pavement rehabilitation treatment for thick AC pavements in poor condition exhibiting extensive severe cracking,
rutting, or other distresses. CIR mix helps to retard reflection cracking. CIR can also be used for pavements that require increased
structural strength. In this case, the additional strength is achieved primarily by an overlay atop the CIR layer.
Candidate pavements for cold-in place recycling are thoroughly evaluated and the properties of the existing AC determined.
Because of the size of a recycling train, CIR is suitable for large projects with room to maneuver.
Typical Service Life and Costs
CIR with an appropriate hot-mix overlay provides a service life of 10 years or more. In situations where the surface layer atop the
CIR mix is a surface treatment, the expected service life is lower. A typical cost of a 4-in.-thick cold recycled AC pavement is about
$9 to $16 per square yard.
Materials and Construction
Cold recycling can be classified by the location where the recycling takes place as:
• Cold in-place recycling (CIR)—All asphalt pavement material processing is completed in situ. CIR is faster and environmentally preferable because of the reduced need to transport materials.
• Cold central plant recycling (CCPR)—Reclaimed asphalt pavement is hauled to a plant site and stockpiled. Subsequently, it is
processed (crushed, screened, and mixed with additives), transported to the job site, and placed and compacted.
CIR can also be classified by the type of the asphalt added to the recycled mix:
• Addition of emulsified asphalt—Traditionally, asphalt emulsion is used to bind the mix. Polymer-modified asphalt emulsions
or polymer-modified high-float emulsions are also used. The total amount of emulsion and water is approximately 4%, the emulsion alone being approximately 1.5%. Because of the added water, the resulting mix requires a minimum 14 days of curing
before the mix can be sealed (overlaid). During this time, the exposed CIR mix can be damaged by traffic. CIR using emulsi-
83
fied asphalt is typically carried out only during the warmer, dryer months. Cooler temperatures and wetter conditions can result
in long curing time during which the cold mix is susceptible to moisture intrusion and abrasion by traffic.
• Addition of expanded (foamed) asphalt—Although the addition of expanded asphalt can be done in-place or off-site, it is typically done in-place. The resulting material is called cold in-place recycled expanded asphalt mix (CIREAM). CIREAM allows
a hot-mix surface course to be placed after only two days of curing. Expanded asphalt mix is less susceptible to environmental
conditions than emulsion mix.
Airport Experience
Only one surveyed airport reported a routine use of cold-in-place recycling. However, the use of CIR is relatively frequent for the
rehabilitation of runways and taxiways on small airports.
84
Fact Sheet 15—Ultra-thin Whitetopping of AC Pavement
Short square slabs
2 to 6 feet
Thin slabs
2 to 4 inches
Milled surface
Existing hot mix asphalt pavement
Ultra-thin Whitetopping Pavement Rehabilitation Method
Ultra-thin whitetopping (UTW) of AC pavements is a rehabilitation method where a thin layer of PCC (2 to 4 in. thick) is bonded to
the milled AC pavement to form a composite pavement structure with a new wearing surface. UTW uses short square slabs, typically
from 2 and 6 ft, as shown in the above illustration.
If the thickness of the PCC overlay is more than 4 and less than 8 in., whitetopping is usually called thin whitetopping; if the thickness exceeds 8 in., it is called conventional whitetopping.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Additional resources include:
ACPA-issued, comprehensive Construction Specification Guidelines for Ultra-thin Whitetopping (IS120).
Rasmussen, R.O. and D.K. Rozycki, NCHRP Synthesis of Highway Practice 338: Thin and Ultra-Thin Whitetopping, Transportation
Research Board of the National Academies, Washington, D.C., 2004.
Saeed, A., M.I. Hammons, and J.W. Hall, “Design, Construction, and Performance Monitoring of Ultra-Thin Whitetopping at a General Aviation Airport,” Proceedings of the 27th International Air Transportation Conference, 2007.
Purpose and Selection Criteria
UTW can be used to rehabilitate AC runways, taxiways, and aprons. It has also been successfully used to mitigate rutting of AC pavements, block cracking, and fuel spill damage, and to increase structural capacity of pavements.
The surface of the existing pavement is cold milled to remove the deteriorated AC pavement. The milled surface also enhances
the bond between the new PCC overlay and the existing AC pavement. The objective is to provide a sound platform for the PCC slab
with a minimum thickness of AC pavement after milling of at least 4 in. A thorough engineering analysis is performed to ensure the
suitability of a UTW overlay. Severe distresses (such as frost heaving and subgrade settlement) are repaired full depth prior to the
placement of UTW. UTW placed on a thick cracked AC layer may result in reflection cracking of PCC slabs.
Typical Service Life and Costs
Preliminary results suggest life spans of 10 years or more. The typical cost of a UTW is estimated to be in the range of $12 to $18 per
square yard.
Materials and Construction
PCC mixes used in UTW overlays are typically high early-strength mixes and generally contain fibers such as polyolefin and
polypropylene. Fibers are expected to increase tensile strength of the mix and improve its resistance to shrinkage and fatigue cracking.
The construction of UTW consists of the following steps:
Pre-overlay repair—Localized repairs may be required to obtain uniform support for UTW.
Surface preparation—Milling of the existing AC is essential for the good performance of the UTW overlay. Milling removes
deteriorated AC and provides a roughened surface that enhances the bond between the remaining AC and the new PCC surface,
thereby creating an integrated pavement layer. Milling is followed by cleaning to remove all debris and any slurry resulting from
85
milling. The typical predominant defect of UTW overlays is corner cracking attributed to the loss of bond between the PCC
slab and the underlying hot-mix asphalt.
PCC placement—Conventional paving practices are used. Ambient temperatures are considered to ensure that UTW concrete is
not placed on an overly hot AC surface. The hot surface could cause the PCC slab to crack when it cools down at night. It could
also reduce the available water (for the chemical hardening process) at the interface of the two materials, thereby reducing the
strength of the PCC at the interface. The AC surface is moistened before the PCC placement to minimize absorption of water
from the PCC mix by AC and to promote bonding.
Texturing—Conventional texturing methods, such as tining, are used.
Curing—Curing is important for all PCC pavements. It is especially important for UTW overlays because of their small thickness
(and large exposure area relative to the volume). Curing compound is placed on all exposed surfaces immediately after texturing and at twice the normal rate.
Joint sawing and sealing—Joint sawing starts as soon as it can be done without significant chipping of the joint edges. Typical
joints are 1 in. deep and 1⁄8 in. wide, and are spaced 2 to 6 ft apart depending on thickness. Joints are not sealed.
Airport Experience
Only a few surveyed airports reported routine use of whitetopping. The Spirit of Saint Louis Airport in Missouri was the first general
aviation airport in the United States to receive an ultra-thin whitetopping in 1995. Since then, whitetopping has been used on both
small and large airports, including the George Bush Intercontinental Airport in Huston.
86
Fact Sheet 16—Joint/Crack Sealing of PCC Pavement
Locate
Clean
Install
Backer rod
Seal
Sequence of Sealing Joints and Cracks in PCC Pavements
Sealing of joints and cracks in PCC pavements is a maintenance treatment that re-seals joints that have missing or poorly performing sealants, and seals major cracks. The sequence of the operation is shown on the above illustration.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division,
Lansing, Apr. 2010.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
Evans, L.D., K.L. Smith, and A.R. Romine, Materials and Procedures for the Repair of Joint Seals in Portland Cement Concrete
Pavements—Manual of Practice, FHWA-RD-99-146, Federal Highway Administration, McLean, Va., 1999.
A comprehensive Concrete Pavement Repair Manual issued by the ACPA in 2003 is available from www.pavement.com.
Engineering Technical Letter 02-8, Silicone Joint Sealant Specification for Airfield Pavements, 2002.
Purpose and Selection Criteria
The purpose of joint and crack sealing is to prevent incompressible materials from getting into joints, and to prevent infiltration of
water and de-icing chemicals into the pavement structure. The presence of incompressible material in the joints can cause spalling
and raveling when the joints close in the summer months. Excess water in the pavement structure can lead to erosion of the base support, and de-icing chemicals can corrode dowels and tie bars.
The objective of resealing is to keep all joints sealed. Typically, only working cracks with the opening (at moderate temperatures)
between 1⁄4 and 1⁄2 in. are sealed. Working cracks are typically transverse and longitudinal cracks. Re-sealing operations are carried out
as scheduled maintenance when more than 50% of transverse joints start to show adhesion failures. Typically, pavements requiring
joint resealing and crack sealing also require other maintenance treatments, such as partial-depth repairs.
Typical Service Life and Costs
There are three main categories of sealants for PCC pavements on the market: hot-poured bituminous sealants, silicone sealants, and
compression seals (preformed or neoprene). Hot-pour sealants have a service life of 8 or more years, silicone sealants 10 years, and
compression seals 12 or more years. The performance of sealants can differ significantly depending on the material and workmanship.
The typical cost of resealing operation is in the range of $3 to $4 per yard for hot-poured rubberized sealant, $4 to $5 per yard for
silicone sealant, and $6 to $7 per yard for compression seals.
Materials and Construction
Typical joint and crack resealing operation consists of the following steps.
Removal of existing sealant—Damaged and underperforming sealant is removed. This may be accomplished by a mechanical
device mounted on a garden-type tractor.
Preparation of sealant reservoir—Typical as-constructed transverse joints have sufficient reservoir at the top of the joint for hotpoured sealant. If the slab faces at the top of the joint do not have sufficient reservoir, the joint may be refaced by diamond saw
cutting. Preformed compression seals require that joint sidewalls are perpendicular and without spalling. In the case of cracks,
the reservoir is created by using a saw equipped with a special crack-sawing blade, rather than by using impact or rotary routers
(e.g., those used for routing AC pavements) that can chip away at the crack face.
87
3 to 6 mm
recess
Depth of
original
saw cut
Sealant
Backer
Rod
Crack
opening
FIGURE B10 Resealed transverse
contraction joint with bituminous sealant
and a backer road.
Cleaning—All debris are cleaned by sand blasting or water blasting to remove all loose and weakened material, and to remove slurry
residue from saw cutting. If sand blasting is used it is followed by air blasting to clean the joint. Joints must be dry before installing
sealant.
Insertion of backer rod—Bituminous sealants may require a device that would prevent a liquid sealant from seeping deep inside
the joint. One such device is a backer rod (Figure B10). The backer rod keeps the sealant in place near the surface of the pavement and prevents bituminous sealant from seeping into the widened crack opening.
Sealant application—The application of hot-poured sealant is similar to the application used for sealing AC pavements. Sealing
operation with compression seals requires the application of a lubricant/adhesive to the joint sidewalls before the insertion of
the seal. Compression seals are typically applied by a specialized machine and primarily used on new pavements. High-modulus
silicone sealants are leveled (tooled) to force the sealant into a full contact with the joint sidewalls and to produce the correct shape
of the sealant on top.
Airport Experience
A majority of surveyed airports reported routine use of silicone sealants, half of the responding airports have used bituminous
sealants, and a minority of responding airports has used neoprene sealants. The silicone sealants as reported by survey respondents
performed best, with all airports reporting very good or good performance. A majority of surveyed airports reported very good or
good performance using bituminous sealants or compression sealants.
88
Fact Sheet 17—Partial-depth (Patch) Repairs of PCC Pavement
Select repairs
Saw cut and
remove material
Apply bonding
agent
Place patching
material
Construction Steps of Partial-depth Repair of PCC Pavement
Partial-depth patch repair of PCC pavements is a maintenance activity that includes removal of damaged material from shallow areas
and replacing it with new PCC material or AC material. The key construction steps involved are shown in the above illustration.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division,
Lansing, Apr. 2010.
Ohio Department of Transportation, Pavement Preventive Maintenance Guidelines, Office of Pavement Engineering, Columbus,
May 2001.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
A comprehensive manual of practice, Concrete Pavement Repair Manual, issued by the ACPA in 2003, is available from
www.pavement.com.
Fowler, D., D. Zollinger, and D. Whitney, Implementing Best Concrete Pavement Spall Repairs, FHWA/TX-08/5-5110-01-1,
National Technical Information Service, Springfield, Va. [Online]. Available: www.ntis.gov.
UFC 3-270-03, Concrete Crack and Partial-Depth Spall Repair, U.S. Department of Defense, Washington, D.C., 2006, 68 pp.
Purpose and Selection Criteria
The purpose of partial-depth repairs is to repair localized shallow areas of damaged pavement, such as joint and corner spalling (joint
chipping, cracking, and breaking), and any loss of material caused by weak concrete. The objective is to prevent further deterioration, restore pavement smoothness, remove the potential for loose material coming off the pavement, and facilitate joint resealing.
Partial-depth repairs are typically done only for surface distresses that affect up to one-half of the slab thickness. Partial-depth
repairs are not suitable for slabs with poor load transfer and areas where reinforcing steel or load transfer devices are exposed. Partialdepth repairs cannot effectively address spalls caused by durability (D) cracking or alkali silica reaction (ASR) damage. If there are
several moderate or severe spalls present along one joint, it may be necessary and more economical to repair the joint using a fulldepth repair.
Partial-depth repairs are often done in combination with full-depth repairs, joint re-sealing and diamond grinding as part of a pavement rehabilitation project.
Typical Service Life and Costs
A partial-depth repair can last as long as the slab itself, typically 10 years or more. A typical cost of a partial-depth repair operation
is in the range of $160 to $220 per square yard.
Materials and Construction
The selection of repair material depends on a number of factors including time constraints, climate, repair size and configuration,
experience with local materials, and future maintenance and rehabilitation plans. Ideal repair materials have similar physical properties, such as elastic modulus, strength, and thermal expansion, as the original concrete. PCC repair materials can be general-use
hydraulic cement or high early-strength hydraulic cement. There are also rapid-set proprietary patching materials on the market.
Bonding agents, if used, are typically sand–cement slurries or epoxy-modified cement slurries. AC material is typically used for temporary repairs only.
89
FIGURE B11 Prepared repair area; the insert, separating the
repair area from the joint, extends beyond the saw cut into the
existing longitudinal joint.
The patching procedure using PCC materials consists of the following steps:
1. Marking the boundaries of deteriorated and/or delaminated concrete.
2. Removal of existing concrete by saw cutting and chipping, or by milling, to create vertical surfaces of the sides of the excavated area.
3. Cleaning of the excavated area by sand blasting or water blasting.
4. Installation of a joint breaker, if the repairs are adjacent to joints, as shown in Figure B11.
5. Application of bonding agent (if used).
6. Placement of the patch material and its consolidation.
7. Finishing and texturing to match surrounding surface.
8. Application of a curing compound to retain moisture.
9. Joint resealing if the patch is adjacent to a joint.
The use of AC material for patching of PCC pavements is considered to be a temporary repair. For this reason, the excavated area is
typically not saw cut and a joint breaker is not installed.
Airport Experience
About one-half of the airports surveyed routinely used or have tried partial-depth repairs with PCC material, a majority of surveyed
airports have used AC material, and a large minority of surveyed airports has used proprietary materials. Overall, the performance of
PCC materials was reported to be better than the performance of AC or proprietary materials.
90
Fact Sheet 18—Full-depth (Patch) Repairs of PCC Pavements
Identify extent
Saw cut
Drill
holes
Insert
Dowels
Place patching
material
Restore base
Sequence of Operation of Full-depth Repair of PCC Pavements
Full-depth patch repair of PCC pavements is a rehabilitation method that involves the full-depth removal of an entire slab or a substantial portion of the entire slab, the installation of load transfer devices (and other reinforcement if applicable), and the replacement
of PCC material. The sequence of the operation is shown on the above illustration.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division,
Lansing, Apr. 2010.
Ohio Department of Transportation, Pavement Preventive Maintenance Guidelines, Office of Pavement Engineering, Columbus,
May 2001.
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
A comprehensive manual of practice, Concrete Pavement Repair Manual, was issued by the ACPA in 2003 and is available from
www.pavement.com.
Concrete Pavement Rehabilitation—Guide for Full-depth Repairs, Report FHWA-RC Atlanta 1/10-03, Resource Center, Federal
Highway Administration, Atlanta, Ga.
Purpose and Selection Criteria
The purpose of full-depth repairs is to repair slabs that can no longer be repaired using partial-depth repairs. This includes slabs with
deteriorated concrete (particularly near joints), corner breaks, mid-slab cracking, slabs damaged by frost heaving and subgrade settlement, slabs with poor load transfer, and slabs where dowels are exposed. The objective of the repair is to restore the smoothness
and structural integrity of the pavement, and to arrest further deterioration.
Full-depth repairs are often done together with other maintenance treatments, such as partial-depth repairs, load transfer restoration, and crack and joint sealing, as part of a pavement rehabilitation project. Full-depth repairs using PCC are also done before overlays.
Typical Service Life and Costs
The full-depth repairs are designed to last as long as the adjacent un-repaired slabs, typically 10 years or more. The typical cost of a
full-depth repair using PCC material is in the range of $160 to $240 per square yard.
Materials and Construction
Full-depth repairs can be done using PCC or AC materials. Patching with AC materials is not considered a permanent repair. When
using PCC materials, depending on the need to open the area to traffic, PCC repair materials can be a conventional PCC paving concrete or a “fast-track” high early-strength mix. Cement mixes modified with the addition of accelerating admixtures, polymers, or
proprietary cement materials are also used. If timing is critical, the use of pre-cast slabs can be considered.
Typical full-depth cast-in-place repair of jointed PCC pavement with dowels consists of the following steps:
Selection of repair boundaries—Full-depth repairs are typically done on the full width of the lane and have the minimum length
of approximately 6 ft. Detailed engineering investigation is required to properly identify the areas requiring full-depth repairs.
Visual examination is not sufficient (Figure B12).
91
Visual deterioration seen on the surface
Existing Joint
Dowel bar
Full-depth
Actual deterioration at bottom of slab
saw cut
Width of the repair area, 6 feet minimum
FIGURE B12 Cross section of deteriorated transverse joint.
Base preparation—After the removal of the deteriorated concrete, the base course, subgrade, and subdrains are restored. Any disturbed base material is re-compacted.
Dowel and tie bar placement—Load transfer across the transverse repair joints is re-established. The illustration at the beginning
of this Fact Sheet shows the sequence of operations for installing dowels. Tie bars may be installed into the side of the PCC
repair area using epoxy; these tie bars will hold the patch to the existing concrete.
Placement of concrete—Before placing concrete, the exposed portion of the dowel bars is coated with a bond breaker. Tie bars
are not coated as it is important for the concrete to bond to the tie bar to prevent separation at the interface between the patch
and the existing concrete.
Finishing and texturing—Unless a grinding operation or an overlay placement is to follow, the patch is textured to resemble the
finish on the rest of the pavement.
Curing—Curing compound is placed as soon as the texturing is completed.
Joint cutting and sealing—All longitudinal and transverse joints are cut and sealed, or resealed.
Pre-Cast Repairs
Pre-cast repairs can provide a good alternative to cast-in-place repairs when it is necessary to minimize the duration of repairs. A new
pre-fabricated concrete slab is placed into the prepared repair area in one piece. The restoration of the load transfer is accomplished
by installing the dowels before or after the slab placement.
Airport Experience
A majority of surveyed airports routinely used or have tried full-depth repairs using PCC or AC materials. A large minority of surveyed airports used proprietary materials. The frequent use of AC materials is surprising and may be the result of the temporary nature
of the repairs and to the low priority for restoring load transfer between PCC slabs on aprons and taxiways. Performance of both AC
and PCC materials was similar, with the majority of surveyed airports reporting very good or good performance. None of the surveyed airports reported using precast panels.
92
Fact Sheet 19—Machine Patching of PCC Pavement with AC Material
1. Rubber tired rollers
2. Static dual steel drum rollers
Hot mix truck
Asphalt distributor
Paver
Optional built-in tack coat application
Optional tack coat
Schematic of Machine Patching Operation of PCC Pavement
Machine patching of PCC pavements is a maintenance technique that involves placing and spreading of AC mix using a paver on
parts of a pavement section. Machine patching includes the preparation of the patching area, addition of the patching material, and
compaction as shown on the illustration above.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Additional resources include:
A comprehensive manual of practice, Concrete Pavement Repair Manual, was issued by the ACPA in 2003 and is available from
www.pavement.com.
Purpose and Selection Criteria
Hot-mix patching of PCC pavements does not substantially improve their structural capacity. Machine patching is most suitable for
repairing surface defects such as map cracking, scaling, loss of pavement friction, and durability cracking. The areas selected for
patching are expected to be well-defined and separated by areas that are in good condition. If the areas requiring patching are closely
spaced, it may be more cost-effective to resurface the entire section.
Machine patching repairs can be divided into permanent and semi-permanent repairs:
Permanent repairs—Permanent patching repairs are used on pavements that are in good condition to improve surface characteristics
and extend the life span. For example, if it is expected that the pavement being repaired will require resurfacing in 6 years, the
patching repair lasting approximately 6 years will be appropriate.
Semi-permanent repairs—Semi-permanent repairs have a limited life expectancy and are typically used when it is anticipated that
the entire pavement will be resurfaced/reconstructed within a few years.
Typical Service Life and Costs
Permanent repairs may last 6 to 10 years or more; semi-permanent repairs may last about 3 to 5 years. A typical cost of machine patching repairs is in the range of $10 to $30 per square yard.
Materials and Construction
Typically, permanent machine patching includes the following steps:
• Removal of the deteriorated PCC material by milling or chipping. Milling may be required to provide a smooth transition
between the original pavement and the patch. Figure B13 shows a construction detail for the start of a long patch applied over
a full width of a facility.
• Application of a tack coat at the sides of the patch and over the entire patched area to improve the bond between the original
pavement and the patch, and to minimize water infiltration.
• Placing of the mix. The placement is done by a paver, and typically in layers not exceeding 3 in. The minimum thickness of a
permanent machine-placed patch is approximately 2 in.
• Compaction of the patch area using rollers.
93
Wedge milling
1¼ inch minimum
2 to 4 feet
Finished overlay
FIGURE B13 Wedge milling to key-in a
2-in.-thick AC patch.
Airport Experience
A few surveyed airports reported on the use of machine patching of PCC pavements with AC routinely; other surveyed airports
reported that they have tried it. Performance data from the survey are incomplete.
94
Fact Sheet 20—Slab Stabilization and Slabjacking
Drill
holes
Inject
grout
Plug
holes
Illustration of Slab Stabilization Procedure
Slab stabilization is a rehabilitation technique that fills voids underneath PCC slabs with grout, but does not raise slabs. Slab stabilization is also called slab subsealing and under-slab grouting. Slabjacking fills voids underneath PCC slabs and raises the grade of
the slabs. The construction sequence is shown on the above illustration
Sources of Information and Additional Resources
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
A comprehensive manual of practice, Concrete Pavement Repair Manual, was issued by the ACPA in 2003 and is available from
www.pavement.com.
Purpose and Selection Criteria
The purpose of slab stabilization is to stabilize a pavement slab by pressurized injection of grout underneath the slab. The objective
is to fill existing voids and restore full slab support, particularly at transverse joints and cracks. The main benefit of subsealing is slowing down the erosion of base and subgrade materials caused by excessive pavement deflections. Slab stabilization is typically carried
out at the first signs of pumping (wetness and discoloration at transverse cracks during wet weather) and before the onset of visible
signs of pavement damage such as corner cracks. Slab stabilization is typically done only for joints and working cracks that exhibit
loss of support.
The purpose of slabjacking is to raise pavement slabs, which have settled over time, back to their original grade by pressurized
injection of grout underneath the slab. At the same time, slabjacking will also stabilize the slab. The objective is to improve pavement smoothness and to fill voids underneath the pavement. Slabjacking can raise PCC slabs by over 2 in.
Slab stabilization and slabjacking are typically carried out concurrently with other rehabilitation techniques such as partial- and
full-depth repairs, diamond grinding, and joint resealing. Slab stabilization is also used to achieve uniform foundation for overlays
and as part of the installation of precast PCC panels.
Typical Service Life and Costs
The expected service life of slab stabilization and slabjacking is 5 to 10 years. The typical cost of slab stabilization is in the range of
$80 to $180 per square yard.
Materials and Construction
Grouting materials used for slab stabilization include portland cement, fly ash-cement, polyurethane, and proprietary products. Typical slab stabilization material consists of a mixture of three parts fly ash and one part Type 10 cement, and water. Important properties of the grout material include the ability to flow into small voids, sufficient strength to support the slab and the load, and long-term
resistance to erosion and deterioration.
Typical slab stabilization operation consists of the following steps:
Location of injection and observation holes—The number of holes depends on the size of the slab. Figure B14 shows an example
pattern of injection and observation holes for the stabilization of transverse joints of a small slab (approximately 15 ft by 20 ft).
Drilling holes—Holes are typically 2 in. in diameter or smaller, and penetrate 2 to 6 in. below the concrete slab. Injection holes
are grouted the same day.
95
Approach Slab
Predominant
direction of
aircraft
Leave Slab
Injection hole
Observation hole
6 feet
1 foot
1.5 feet
FIGURE B14 Typical location of injection
and observation holes for the stabilization of
a transverse joint; altogether there are five
injection holes and two observation holes
per slab.
Grout injection—During the grout injection process, vertical movement of the slabs is continuously monitored. The injection
process is complete when grout undiluted with water appears in the observation holes, when the slab begins to rise, or when
no grout material is injected at the maximum allowable pressure (typically 100 psi).
Plugging and cleanup—After injecting one hole, the hole is immediately temporarily plugged. After all holes are injected, the
temporary plugs are removed and the holes are filled flush with cement grout.
Verification testing—After a minimum of 24 h, slabs are retested for the presence of voids and load transfer efficiency. It is possible to repeat the slab stabilization operation if the first attempt is insufficient. In this case, a new set of injection and observation holes is used.
Slabjacking process is similar to the slab stabilization process. However, the injection of grout continues until the slab reaches the
desired grade.
Airport Experience
One surveyed airport reported routine use of slab sub-sealing. A small minority of surveyed airports has tried slab sub-sealing. Performance data from the survey are insufficient.
96
Fact Sheet 21—Load Transfer Restoration
Slots with Dowel Bars for Load Transfer Restoration
Load transfer restoration is a rehabilitation method that restores the ability of the concrete slabs to transfer wheel loads across transverse joints. The illustration above shows three slots with dowel bars prior to grouting (Source: Pierce et al. 2009).
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Michigan Department of Transportation, Capital Preventive Maintenance, 2003 ed., Construction and Technology Division,
Lansing, Apr. 2010.
Additional resources include:
The FHWA in conjunction with the ACPA has issued a useful publication entitled Guide for Load Transfer Restoration. ACPA
also issued as a useful guide Stitching Concrete Pavement Cracks and Joints, Special Report SR903P [Online]. Available:
www.pavement.com.
Pierce, L.M., J. Weston, and J.S. Uhlmeyer, Dowel Bar Retrofit—Do’s and Don’ts, Report No. WA-RD 576.2, Washington State Department of Transportation, Olympia, Mar. 2009.
Purpose and Selection Criteria
Load transfer restoration (also called dowel bar retrofit) is achieved by inserting tie bars across the transverse joints of jointed PCC
pavements. The objective is to increase load transfer across joints.
Load transfer restoration is suitable for pavements with the load transfer efficiency of 60% or less, early signs of faulting (typically
more than 0.1 inch but less than 0.4 inch), and with adequate slab thickness. To ensure proper selection of transverse joints that would
benefit from load transfer restoration, evaluation of the load transfer efficiency is typically carried out using Falling Weight Deflectometer (FWD) testing. Load transfer restoration is typically done concurrently with other rehabilitation treatments such as full-depth
repairs and resealing of joints. It is also used prior to overlays.
Typical Service Life and Costs
The estimated service life for load transfer restoration is between 5 and 15 years. The typical cost of a load transfer restoration or
crack stitching is on the order of $50 to $100 per dowel bar or tie bar.
Materials and Construction
The procedure of load transfer restoration includes the following steps:
Selecting joints—The selection is normally based on FWD testing. Some joints may not require any repairs, and some joints may
require full-depth repair rather than load transfer restoration.
97
Cross sectional view
Longitudinal view
Mill or
saw cut
2½ inches (min)
4 inches (max)
As required
15 – 2 0 inches
T/2
T
Full depth
joint insert
Expansion
dowel bar cap
FIGURE B15 Placement of a dowel in the
slots. Dowel is placed on a support chair and
is approximately 1⁄2 in. above the bottom of
the slot.
Slot cutting—A diamond-tipped slot cutting saw has become the most common equipment for slot cutting, although modified
milling machines have been also used. It is important that the slots are perpendicular to the transverse joint, are large enough
to place the dowel at mid-depth of the slab and allow for the backfill material to flow under and around the dowel, and are properly cleaned by sand blasting followed by air blasting.
Insertion of dowels—The most common type of load transfer device is a smooth epoxy-coated dowel bar. The size of the dowel
bars depends on the slab thickness and anticipated loads. Typically, dowel bars have the diameter of 1 to 3⁄4 in. and a length of
15 to 20 in. (Figure B15). One-half of the dowel bar is coated with a bond-breaking agent.
Backfilling the slots—It is important that backfill materials do not exhibit excessive shrinkage. For some installations, emphasis
is placed on backfill materials that develop early strength to facilitate timely opening of the pavement to traffic. Polymer concretes and high early-strength PCC materials have been used in most installations to date.
Airport Experience
About one-quarter of surveyed airports report routine use or have tried dowel retrofit. Performance data from the survey are insufficient.
98
Fact Sheet 22—Crack and Joint Stitching
Identify
cracks
Drill
holes
Insert
tie bar
Grout
holes
Illustration of Steps in Crack and Joint Stitching
Crack stitching is a rehabilitation method that repairs longitudinal and meandering cracks, and nonworking transverse cracks. Joint
stitching strengthens longitudinal joints. There are two crack stitching methods: cross stitching and slot stitching. The illustration
above shows an operational sequence of cross stitching of a longitudinal crack.
Sources of Information and Additional Resources
Gransberg, D.D., “Life-Cycle Cost Analysis of Surface Retexturing with Shotblasting as an Asphalt Pavement Preservation Tool,”
Transportation Research Record: Journal of the Transportation Research Board, No. 2108, Transportation Research Board of
the National Academies, Washington, D.C., 2009, pp. 46–52.
Additional resources include:
The FHWA in conjunction with the ACPA has issued a useful publication entitled Guide for Load Transfer Restoration. ACPA has
also issued Stitching Concrete Pavement Cracks and Joints, Special Report SR903P, which is available at: www.pavement.com.
Pierce, L.M., J. Weston, and J.S. Uhlmeyer, Dowel Bar Retrofit—Do’s and Don’ts, Report No. WA-RD 576.2, Washington State
Department of Transportation, Olympia, Mar. 2009.
Purpose and Selection Criteria
Crack and joint stitching is done by inserting tie bars across cracks or joints. This prevents widening of cracks and joints (slab migration). Narrow cracks maintain aggregate interlock, reduce the potential for faulting, and are easier to seal. Good candidates for crack
stitching are pavements in good condition where longitudinal cracks and joints show signs of slab migration. If longitudinal cracks
and joints perform well simply by sealing them, crack and joint stitching may not be necessary.
Typical Service Life and Costs
The estimated service life for crack stitching is 5 to 15 years. A pioneering crack stitching application on a highway pavement was
still performing well after 15 years. A typical cost of crack stitching is in the order of $60 to $120 per dowel bar or tie bar.
Stitching of Cracks and Joints
Stitching of cracks using slot stitching is very similar to load transfer restoration with the following main exceptions:
• Stitching is done to repair longitudinal and meandering cracks, nonworking transverse cracks, and longitudinal joints.
• Deformed tie bars with a smaller diameter are used instead of smooth dowel bars and are placed further apart than dowel bars.
• Tie bars are not coated with a bond-breaking agent.
Cross stitching includes the following steps:
•
•
•
•
•
Drilling holes at a 35° to 45° angle so that they intersect the longitudinal crack or joint at about the slab mid-depth (Figure B16).
Cleaning of holes by air blasting.
Injecting epoxy into the hole in a sufficient amount to fill all the available space after a tie bar is inserted.
Inserting a tie bar into the hole, leaving approximately 1 in. between the pavement surface and the end of the tie bar.
Removing excess epoxy and finishing it flush with the pavement.
Airport Experience
A small minority of surveyed airports reported routine or trial use of crack and joint stitching. Performance data from the survey are
insufficient.
99
Plan view
Cross sectional view
Deformed tie bars inserted
and grouted into drilled holes
(diameter is typically ¾ inch)
@ 24 inches
inch
35º – 45º
PCC Slab
Dowel bar
Drill hole
Base
Longitudinal Crack
Longitudinal Crack
FIGURE B16 Stitched longitudinal crack.
100
Fact Sheet 23—AC Overlays of PCC Pavements
1. Optional vibratory drum rollers
2. Rubber tired rollers
3. Static dual steel drum rollers
Paver
Optional load
transfer vehicle
Hot mix truck
Asphalt distributor
Pre-overlay
repairs
Tack coat application
Schematic of Paving Operation for Asphalt Overlay of PCC Pavement
AC overlay of PCC pavements is a rehabilitation technique that includes repairs of structural deficiencies in the existing PCC slab,
application of a bonding agent (tack coat) and/or a layer intended to mitigate the propagation of reflection cracking, and placement
of a hot-mix asphalt overlay. The construction sequence is illustrated above.
Sources of Information and Additional Resources
California Department of Transportation, Maintenance Technical Advisory Guide, 2nd ed., Office of Pavement Preservation, Division
of Maintenance, Sacramento, 2008.
Additional resources include:
The Asphalt Institute has issued a useful publication entitled Asphalt Overlays for Highway and Street Rehabilitation, Manual Series
No. 17, Lexington, Ky., 1998.
Purpose and Selection Criteria
AC overlays of PCC pavements can be classified as functional overlays and structural overlays.
Functional overlays—The purpose of functional overlays is to improve functional deficiencies of the PCC pavement such as low
pavement surface friction, inadequate cross-slope, and roughness. However, if roughness is caused primarily by slab stepping
(faulting), a functional overlay may not be a cost-effective solution. The thickness of functional overlays ranges from 2 to about
3 in. Functional overlays are suitable for pavements in good structural condition without progressive faulting or for pavements
that can be effectively brought to good structural condition by a limited amount of load transfer restoration, slab stabilization,
and full-depth patching.
Structural overlays—The purpose of structural overlays is not only to improve the functional deficiencies, but also to improve the
structural capacity of the entire pavement. The improvement in the structural strength of the pavement may be required because
the structural capacity has been inadequate or is expected to be inadequate considering future aircraft operations.
Typical Service Life and Costs
The typical service life of AC overlays over PCC pavement is 8 to 15 years. Cost can range widely depending on the overlay thickness and on the treatment of the existing PCC pavement. Considering that a typical cost of hot mix is $60 to $90 per ton, a 4-in.-thick
overlay will cost $12 to $18 per square yard. However, this cost does not include any rehabilitation of the underlying PCC pavement
that may be required before placing the overlay.
Materials and Construction
Materials used for hot-mix overlay of PCC pavements are similar to those used for hot-mix overlay of AC pavements and are
described in Fact Sheet 12, Hot Mix Overlay of AC Pavement.
The main challenge in constructing hot-mix overlay of jointed PCC pavements is the prevention or reduction of reflection cracking and the subsequent deterioration of reflection cracks. Over the years, many methods and materials have been developed and field
tested. Some of these methods, arranged in the order of increasing costs, include:
Tack coat—Tack coat will not significantly affect reflection cracking, but will improve the bond of hot mix with the PCC surface
and thus will reduce the potential for delaminating near the reflection cracks.
101
Hot mix overlay
Old JPCP
Pavement
Crack arresting
interlayer
Base
Subgrade Soil
FIGURE B17 Crack arresting
granular interlayer.
Sawing and sealing of joints in the overlay—Sawing is done directly above the joints in the underlying PCC pavement and the
saw cuts are sealed with liquid asphalt or joint sealant material. This technique prevents uncontrolled reflective cracking and
provides joints that can be maintained.
Stress relieving interlayers—A number of products designed to reduce stress in the overlays caused by joint movements have been
tested. These products include geotextile fabrics and rubber or polymer-modified tack coats (with or without cover aggregate)
and surface treatments used singly or in various combinations.
Crack arresting interlayers—Crack arresting interlayers are typically bound and unbound aggregate layers containing large
aggregate particles. The thickness of the interlayer is typically more than 4 in., and the layer contains crushed open-graded
aggregate with large numbers of voids (see Figure B17).
Increased overlay thickness—The increased overlay thickness delays the appearance of reflection cracks on the pavement surface. Typically, cracks propagate through the overlay at the rate of approximately 1⁄2 to 3⁄4 in. per year.
Pre-overlay repairs—Repairs include slab repairs (slab stabilization, load transfer restoration, full-depth repairs) and improving
drainage (retrofit subdrains).
Fracturing the PCC slabs—The methods include crack-and-seat and rubblization.
Airport Experience
Nearly one-half of the surveyed airports reported using AC overlays of PCC pavements routinely or have tried them. All surveyed
airports that have used AC overlays rated their performance as very good or good.
102
Fact Sheet 24—Bonded PCC Overlay of PCC Pavements
Matching joints
PCC overly
Bonding agent
Original PCC pavement
Illustration of Bonded PCC Overlay
Bonded PCC overlay of PCC pavements is a rehabilitation technique that features the placement of a thin PCC overlay directly on
the surface of the existing PCC pavement with the overlay bonded to the existing pavement. Bonded overlays are typically 2 to 5 in.
thick and are constructed as jointed plain concrete pavements with transverse and longitudinal joints matching those in the underlying pavement as shown in the illustration above.
Sources of Information and Additional Resources
Hicks, R.G., S.B. Seeds, and D.G. Peshkin, Selecting a Preventive Maintenance Treatment for Flexible Pavements, Publication
FHWA-IF-00-027, Federal Highway Administration, U.S. Department of Transportation, Washington, D.C., 2000.
Additional resources include:
Up-to-date information on design, construction, and performance of PCCP overlays is summarized in Portland Cement Concrete
Overlays, State of the Art Technology Synthesis, Publication FHWA-IF-02-045, U.S. Department of Transportation, Federal
Highway Administration, Apr. 2002.
ACPA document TB-007 P, Guidelines for Bonded Concrete Overlays, provides useful practical guidelines.
Saeed, A., M.I. Hammons, and J.W. Hall, “Design, Construction, and Performance Monitoring of Ultra-Thin Whitetopping at a General Aviation Airport,” Proceedings of the 27th International Air Transportation Conference, Advancing Airfield Pavements,
American Society of Civil Engineers, Reston, Va., 2007.
Purpose and Selection Criteria
The purpose of the bonded PCC overlay is to improve pavement smoothness and pavement surface friction and to provide increased
structural strength of the pavement. Most bonded PCC overlays are placed on jointed plain concrete pavements, and such placement
is assumed herein.
A bonded overlay is an appropriate rehabilitation method if the structural strength of the pavement needs to be increased, and the
existing PCC pavement is in a condition conducive to such a treatment. The need for the overlay is based on an anticipated increase
in aircraft loads (more and/or heavier aircraft). If load-associated pavement defects are already visible, a bonded overlay is not an
appropriate rehabilitation technique. Even though bonded overlays increase structural capacity of the pavement, they are unable to
arrest progression of faulting. A bonded overlay is also inappropriate if durability-related defects are present, such as scaling and
D-cracking. These defects limit the ability of the overlay to bond with its base.
Typical Service Life and Costs
The expected service life of bonded overlays is approximately 10 to 20 years, and their cost is approximately $15 to $25 per square
yard for a 4-in.-thick overlay.
Materials and Construction
Bonded overlays usually use conventional PCCP paving mixes. Bonded overlays may also utilize high early-strength PCCP mixes and
mixes containing polypropylene and other fibers. The construction of a bonded overlay consists of the following construction tasks:
Pre-overlay repairs—Bonded overlay is placed over pavements in good structural condition. However, some localized repairs
may be required such as partial-depth repairs, full-depth patching, and load transfer restoration. All cracks (corner, longitudinal,
or transverse) in the underlying pavement are repaired.
103
Saw cut reservoir for sealant
Bonded overlay
Dowel bar
Saw cut joint
Bonding
agent
Old JPCP
pavement
Base
Subgrade soil
FIGURE B18 Cross section of bonded
overlay of jointed plain concrete pavement
Surface preparation—It is essential to ensure that the bonded overlay slab and the slab underneath act as one monolithic slab. The
existing concrete surface is cleaned and roughened through a mechanical process that removes a thin layer of concrete. The
most commonly used procedures are shot blasting or micromilling followed by air blasting. A bonding agent is applied just
prior to paving; a commonly used bonding agent is a mixture of cement and water; this slurry is placed immediately in front
of the paver.
PCC placement, finishing, texturing, and curing—The placement of a bonded overlay and texturing uses conventional procedures.
It is very important that the bonding agent not dry out prior to placement of new concrete. Proper curing is also important
because of the large surface area of the overlay relative to its thickness. A higher than usual application rate of a curing compound is typically used.
Joint construction and sealing—It is important to locate the transverse and longitudinal joints of the bonded overlay directly above
those in the underlying pavement, with the deviation not exceeding 1 in. Transverse joints are sawn through the entire slab
thickness plus additional 1⁄2 in. to ensure a complete slab separation. Longitudinal joints are sawed to one-half of the slab thickness. Sawing is done as soon as possible and the joints are sealed. Sealing requires additional saw cutting to create a reservoir
on the top of the pavement and filling the reservoir with sealant (Figure B18).
Airport Experience
A few surveyed airports reported the use of bonded overlays routinely or have tried them. Performance data from the survey are
incomplete.
Abbreviations used without definitions in TRB publications:
AAAE
AASHO
AASHTO
ACI–NA
ACRP
ADA
APTA
ASCE
ASME
ASTM
ATA
ATA
CTAA
CTBSSP
DHS
DOE
EPA
FAA
FHWA
FMCSA
FRA
FTA
HMCRP
IEEE
ISTEA
ITE
NASA
NASAO
NCFRP
NCHRP
NHTSA
NTSB
PHMSA
RITA
SAE
SAFETEA-LU
TCRP
TEA-21
TRB
TSA
U.S.DOT
American Association of Airport Executives
American Association of State Highway Officials
American Association of State Highway and Transportation Officials
Airports Council International–North America
Airport Cooperative Research Program
Americans with Disabilities Act
American Public Transportation Association
American Society of Civil Engineers
American Society of Mechanical Engineers
American Society for Testing and Materials
Air Transport Association
American Trucking Associations
Community Transportation Association of America
Commercial Truck and Bus Safety Synthesis Program
Department of Homeland Security
Department of Energy
Environmental Protection Agency
Federal Aviation Administration
Federal Highway Administration
Federal Motor Carrier Safety Administration
Federal Railroad Administration
Federal Transit Administration
Hazardous Materials Cooperative Research Program
Institute of Electrical and Electronics Engineers
Intermodal Surface Transportation Efficiency Act of 1991
Institute of Transportation Engineers
National Aeronautics and Space Administration
National Association of State Aviation Officials
National Cooperative Freight Research Program
National Cooperative Highway Research Program
National Highway Traffic Safety Administration
National Transportation Safety Board
Pipeline and Hazardous Materials Safety Administration
Research and Innovative Technology Administration
Society of Automotive Engineers
Safe, Accountable, Flexible, Efficient Transportation Equity Act:
A Legacy for Users (2005)
Transit Cooperative Research Program
Transportation Equity Act for the 21st Century (1998)
Transportation Research Board
Transportation Security Administration
United States Department of Transportation