Guide for Conducting Forensic Investigations of Highway Pavements (2013)

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N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP REPORT 747 Guide for Conducting Forensic Investigations of Highway Pavements Gonzalo R. Rada AMEC EnvironMEnt & infrAstruCturE, inC. Beltsville, MD David J. Jones John T. Harvey univErsity of CAliforniA Davis, CA Kevin A. Senn niChols Consulting EnginEErs, Chtd. Reno, NV Mark Thomas fugro ConsultAnts, inC. Austin, TX Subscriber Categories Pavements • Materials TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2013 www.TRB.org Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board’s recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or duplicate other highway research programs. Published reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from: Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 747 Project 01-49 ISSN 0077-5614 ISBN 978-0-309-28345-8 Library of Congress Control Number 2013944805 © 2013 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, AASHTO, FAA, FHWA, FMCSA, FTA, or Transit Development Corporation 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 National Cooperative Highway 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 National Cooperative Highway 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.

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Board’s varied activities annually engage about 7,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individu- als interested in the development of transportation. www.TRB.org www.national-academies.org

C O O P E R A T I V E R E S E A R C H P R O G R A M S AUTHOR ACKNOWLEDGMENTS The preparation of this guide was performed under NCHRP Project 01-49 by Fugro Consultants, Inc. Dr. Gonzalo R. Rada of AMEC Environment and Infrastructure, Inc., formerly of Fugro, served as the Principal Investigator. The other authors of this guide included Dr. David J. Jones and Dr. John T. Harvey with the University of California, Davis; Mr. Kevin A. Senn of Nichols Consulting Engineers, Chtd.; and Mr. Mark Thomas of Fugro. CRP STAFF FOR NCHRP REPORT 747 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Amir N. Hanna, Senior Program Officer Andréa Harrell, Senior Program Assistant Eileen P. Delaney, Director of Publications Natassja Linzau, Editor NCHRP PROJECT 01-49 PANEL Field of Design—Area of Pavements Roger L. Green, Pickerington, OH (formerly with Ohio DOT)(Chair) Luis Julian Bendana, Rochester, NY (formerly with New York State DOT) Dar-Hao Chen, Texas DOT, Austin, TX Judith B. Corley-Lay, North Carolina DOT, Raleigh, NC Mohamed K. Elfino, Virginia DOT, Richmond, VA Elizabeth A. Hunt, Oregon DOT, Salem, OR Daniel P. Johnston, Pierre, SD (formerly with South Dakota DOT) Ray K. Moore, Round Rock, TX (formerly with the University of Nebraska-Lincoln) Aramis Lopez, FHWA Liaison Stephen F. Maher, TRB Liaison

F O R E W O R D By Amir N. Hanna Staff Officer Transportation Research Board This report presents a recommended Guide for Conducting Forensic Investigations of High- way Pavements. The guide includes a practical and logical process for conducting forensic investigations of pavements to help understand the reasons behind premature failures or exceptionally good performance, and to collect data for use in developing or calibrating performance-prediction models. The information obtained from these investigations will provide a basis for improving pavement design and construction practices. The material contained in the report will be of immediate interest to state materials, pavement, and construction engineers, design consultants, paving contractors, and others involved in the different aspects of pavement design and construction. Forensic investigations of highway pavements are generally conducted to (1) investigate underlying causes of premature pavement failures; (2) understand the factors contributing to exceptional pavement performance and longevity; and (3) collect data to support devel- opment and/or calibration of performance prediction models. Although forensic investiga- tions have frequently been conducted by highway agencies, these investigations have often been conducted following different practices and have focused on a specific issue, and their processes and findings have not been adequately documented, making it difficult to use the generated data in other studies. In addition, there are no widely accepted guidelines for con- ducting these investigations that consider relevant factors, such as functional and structural performance, material-related distress, pavement type, sampling and testing requirements, and sequence of activities. Research was needed to identify and evaluate current practices for conducting forensic investigations and develop a rational process that consider all rel- evant factors and provide a realistic means for conducting these investigations. Also, there was a need to incorporate this process into a Guide for Conducting Forensic Investigations of Highway Pavements to help highway agencies conduct cost-effective investigations that will enhance understanding of pavement performance and provide the necessary data for improving pavement design and analysis procedures and construction practices. Under NCHRP Project 1-49, “Guidelines for Conducting Forensic Investigation of High- way Pavements,” Fugro Consultants, Inc. of Austin, Texas worked with the objective of developing a Guide for Conducting Forensic Investigations of Highway Pavements. In pursuing this objective, the research recognized that forensic investigations are generally concerned with acquiring and evaluating data to identify the causes of premature pavement failure; understand the factors contributing to longevity of pavements; and document/understand observed performance and support development and/or calibration of performance pre- diction models (e.g., for use in local calibration of the models contained in the AASHTO Pavement ME—the Mechanistic-Empirical Pavement Design Guide [MEPDG]). The data

acquired from these investigations can then be used to enhance pavement design and con- struction practices. To accomplish this objective, the research identified and evaluated tra- ditional and innovative processes for conducting forensic investigations of pavements and incorporated the best practices into a rational Guide for Conducting Forensic Investigations of Highway Pavements. The process contained in the guide is structured in three phases to allow review after each phase and identify the most appropriate actions for subsequent phases. In this manner, actions that optimize use of resources and enhance the potential for achieving the investigation’s objective will be identified and implemented. The process is supplemented by examples of pavement investigations to illustrate the application of the guide and a set of forms to facilitate recording and use of the acquired data. A summary of the research performed to develop the guide is presented as an attachment to the guide.

C O N T E N T S 1 Chapter 1 Introduction 1 1.1 Background 2 1.2 Objective 2 1.3 Scope 2 1.4 Investigation Approach 3 1.5 Organization of the Guide 5 Chapter 2 General Investigation Philosophy 5 2.1 Understanding Pavement Performance 6 2.2 Recognizing Data and Information Needs 8 2.3 Avoiding Premature Conclusions 8 2.4 Pavement Performance Investigation Scenarios 9 2.5 Investigation Phases 13 Chapter 3 Investigation Request and Preliminary Investigation 13 3.1 Preparing a Forensic Investigation Request 13 3.2 Evaluating a Forensic Investigation Request 14 3.3 Record of Decision to Proceed or Not to Proceed with Investigation 14 3.4 Initiating a Forensic Investigation 14 3.5 Undertaking the Preliminary Investigation 16 3.6 Preparing a Preliminary Investigation Report and Record of Decision 17 Chapter 4 Initial Forensic Investigation Plan 17 4.1 Selecting a Project Investigation Team 19 4.2 Pre-Investigation Site Visit 27 4.3 Preparing a Cost Estimate 27 4.4 Writing an Initial Investigation Plan 28 4.5 Approval of Initial Investigation Plan and Record of Decision 29 Chapter 5 Non-Destructive Testing 29 5.1 Implementing the Initial Investigation Plan 29 5.2 Non-Destructive Testing Analysis 38 5.3 Interim Report 38 5.4 Decision to Continue or Terminate the Study 39 Chapter 6 Final Investigation Plan 39 6.1 Finalizing the Investigation Plan 42 6.2 Approval of the Final Investigation Plan and Record of Decision 43 Chapter 7 Destructive and Laboratory Testing 43 7.1 Investigation Arrangements 43 7.2 Visual Assessments 45 7.3 Key Issues Concerning Destructive Testing 58 7.4 Key Issues Concerning Laboratory Testing

60 Chapter 8 Data Analysis, Hypothesis Testing, and Final Report 60 8.1 Data Analysis and Hypothesis Testing 61 8.2 Forensic Investigation Report 61 8.3 Record of Decision 62 Chapter 9 Investigation Close-Out 62 9.1 Investigation Review 62 9.2 Actions Resulting from the Forensic Investigation 63 9.3 Investigation Close-Out 64 References 65 Appendix A Generic Issues 72 Appendix B Case Studies 83 Appendix C Example Forms 129 Appendix D Example Checklists 136 Attachment Guide for Conducting Forensic Investigations of Highway Pavements: Background Research Note: Many of the photographs, figures, and tables in this report have been converted from color to grayscale for printing. The electronic version of the report (posted on the Web at www.trb.org) retains the color versions.