Evaluation of Indirect Tensile Test (IDT) Procedures for Low-Temperature Performance of Hot Mix Asphalt (2004)

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T R A N S P O R T A T I O N R E S E A R C H B O A R D WASHINGTON, D.C. 2004 www.TRB.org NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 530 Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration SUBJECT AREAS Materials and Construction Evaluation of Indirect Tensile Test (IDT) Procedures for Low-Temperature Performance of Hot Mix Asphalt D. W. CHRISTENSEN R. F. BONAQUIST Advanced Asphalt Technologies, LLC Sterling, VA

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. Note: The Transportation Research Board of the National Academies, the National Research Council, the Federal Highway Administration, the American Association of State Highway and Transportation Officials, and the individual states participating in 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 this report. 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 530 Project D9-29 FY’01 ISSN 0077-5614 ISBN 0-309-08808-9 Library of Congress Control Number 2004111929 © 2004 Transportation Research Board Price $20.00 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. Such approval reflects the Governing Board’s judgment that the program concerned is of national importance and appropriate with respect to both the purposes and resources of the National Research Council. The members of the technical committee selected to monitor this project and to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the project. The opinions and conclusions expressed or implied are those of the research agency that performed the research, and, while they have been accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National Research Council, the American Association of State Highway and Transportation Officials, or the Federal Highway Administration, U.S. Department of Transportation. Each report is reviewed and accepted for publication by the technical committee according to procedures established and monitored by the Transportation Research Board Executive Committee and the Governing Board of the National Research Council.

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished schol- ars 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 techni- cal matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Acad- emy 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 achieve- ments of engineers. Dr. William A. Wulf 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 Acad- emy, 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 the Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is a division of the National Research Council, which serves the National Academy of Sciences and the National Academy of Engineering. The Board’s mission is to promote innovation and progress in transportation through research. In an objective and interdisciplinary setting, the Board facilitates the sharing of information on transportation practice and policy by researchers and practitioners; stimulates research and offers research management services that promote technical excellence; provides expert advice on transportation policy and programs; and disseminates research results broadly and encourages their implementation. The Board’s varied activities annually engage more than 5,000 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 individuals interested in the development of transportation. www.TRB.org www.national-academies.org

COOPERATIVE RESEARCH PROGRAMS STAFF FOR NCHRP REPORT 530 ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, Manager, NCHRP EDWARD T. HARRIGAN, Senior Program Officer EILEEN P. DELANEY, Director of Publications ELLEN M. CHAFEE, Assistant Editor NCHRP PROJECT D9-29 PANEL Field of Materials and Construction—Area of Bituminous Materials LARRY L. MICHAEL, Maryland State Highway Administration (Chair) RONALD COMINSKY, Pennsylvania Asphalt Pavement Associations, Harrisburg, PA GARY A. FREDRICK, New York State DOT CINDY LAFLEUR, Callanan Industries, Inc., Albany, NY DEAN A. MAURER, Pennsylvania DOT MURARI M. PRADHAN, Utah DOT JOHN “JACK” WEIGEL, JR., Payne & Dolan, Inc., Waukesha, WI THOMAS HARMAN, FHWA Liaison Representative JOHN D’ANGELO, FHWA Liaison Representative LESLIE ANN MYERS, FHWA Liaison Representative FREDERICK HEJL, TRB Liaison Representative AUTHOR ACKNOWLEDGMENTS The research documented in this report was performed under NCHRP Project 9-29 by Advanced Asphalt Technologies, LLC (AAT). Ramon Bonaquist, Ph.D., P.E., and Chief Operating Offi- cer for AAT, served as Principal Investigator. Donald W. Chris- tensen, Jr., Ph.D., P.E., and Senior Engineer for Advanced Asphalt Technologies, LLC, was responsible for conducting the work doc- umented in this report. Substantial data gathered with the indirect tensile test device have been summarized and analyzed in this report. These data were submitted by six different laboratories, both public and private, located throughout the United States. AAT sin- cerely thanks the organizations and individuals for their coopera- tion. Because several of the participating laboratories requested anonymity, the parties involved unfortunately cannot be individu- ally acknowledged.

This report presents the findings of a research project to evaluate the use of the indi- rect tensile creep and strength test procedures in AASHTO Standard Method of Test T322-03 in mixture and structural design methods for hot mix asphalt. The report will be of particular interest to pavement design and materials engineers in state highway agencies, as well as to materials suppliers and paving contractor personnel who are responsible for the design and evaluation of hot mix asphalt mixtures and pavements. The prevention of the low-temperature cracking (also called thermal cracking) in hot mix asphalt (HMA) pavements is a critical issue for many transportation agencies in the United States and Canada. In the Superpave mix design method developed in the Strategic Highway Research Program (SHRP), this type of distress is addressed through the selection of an appropriate performance grade of asphalt binder and the evaluation of candidate mix designs with the indirect tensile (IDT) creep and strength procedure developed in SHRP Project A-003A by Roque and his co-workers at the Pennsylvania State University. At the conclusion of SHRP, Roque’s IDT procedure was first codified as AASHTO provisional method of test TP9 and then adopted by AASHTO as Standard Method of Test T322-03, Determining the Creep Compliance and Strength of Hot Mix Asphalt (HMA) Using the Indirect Tensile Test Device. NCHRP Project 9-19 subse- quently identified AASHTO T322 as a suitable simple performance test for low- temperature cracking in HMA mix design, and the same procedure was selected in NCHRP Project 1-37A as the materials characterization test method for the predic- tion of low-temperature cracking of flexible pavements in the recently completed Mechanistic-Empirical Pavement Design Guide. During the 1993-1998 Superpave implementation program, the Federal Highway Administration (FHWA) developed equipment specifications and procured six IDT devices as part of a national pooled fund procurement. This equipment was located at the FHWA’s Turner Fairbank Highway Research Center and the five Superpave Regional Centers. The IDT strength test underwent ruggedness testing by the FHWA, the Asphalt Institute, and the Superpave Regional Centers as part of NCHRP Project 90-06. In addition, the IDT was used in the design and analysis of HMA used in Wes- Track, MnROAD, FHWA ALF, and many in-service field projects incorporating Superpave-designed HMA. Other private- and public-sector organizations have used the IDT on a continuing basis and have accumulated considerable test data and derived material properties. Work has also been conducted to examine whether TP9 can be per- formed with simpler, less expensive equipment than the current IDT device. The states, however, have been hesitant to proceed with procurement of this test equipment until such time as the available information was fully analyzed and the test procedure fully evaluated. FOREWORD By Edward T. Harrigan Senior Program Officer Transportation Research Board

Under Phase III of NCHRP Project 9-29, “Simple Performance Tester for Super- pave Mix Design,” Advanced Asphalt Technologies LLC was assigned the task of eval- uating and refining the indirect tensile test (IDT) procedures in AASHTO Standard Method Test T322. In conducting the research, Advanced Asphalt Technologies (1) critically reviewed the procedures and equipment for performing the IDT creep and strength tests; (2) analyzed IDT creep and strength data sets collected by various pub- lic and private sector laboratories to determine whether there are significant differences among the data related to the equipment configuration, the details of the test method, or the method of data reduction and analysis; and (3) critically examined the theoreti- cal basis of IDT test and data reduction methods recommended for structural and mix design in Projects 1-37A and 9-19. Based on the results of this research, the project team suggested several specific changes to AASHTO T322 to reduce its variability and improve the precision and reli- ability of its results as both a simple performance test in HMA mix design and a mate- rials characterization test for structural design. In particular, further standardization of the IDT creep procedure and equipment is recommended to further improve its preci- sion. The research also found that the equation developed in the SHRP asphalt research program to estimate the HMA coefficient of thermal contraction is not accurate and should be abandoned. A simple, improved procedure for estimating this coefficient was developed that is relatively accurate compared with measured results. Finally, estimates of creep compliance and strength obtained from asphalt binder and mixture volumet- ric data with the Hirsch model were found to provide good agreement with values mea- sured with AASHTO T322. Such estimates may be useful in situations where time, money, or both are not available to conduct IDT creep and strength tests, or for field quality control purposes. This final report includes a detailed description of the experimental plan, a discus- sion of the research results, and two supporting appendixes: • Appendix A: Review of AASHTO T322 and Recent Proposed Changes • Appendix B: Equipment Configurations for Creep and Strength Testing of Hot Mix Asphalt Concrete at Low Temperatures Appendix C: Summary Data for Laboratory Testing Program is available for loan on request from NCHRP. The research results have been referred to the TRB Mixtures and Aggregate Expert Task Group for its review and possible recommendation to the AASHTO Highway Subcommittee on Materials for adoption of the suggested changes to AASHTO T322 presented in Appendix A.

1 SUMMARY 3 CHAPTER 1 Introduction and Research Approach Problem Statement and Research Objective, 3 Scope of Study, 3 Research Approach, 3 5 CHAPTER 2 Findings Review of AASHTO T322, 5 Experience with the IDT Test at the Regional Superpave Centers, 7 Refinements in the IDT Test During NCHRP Projects 1-37A and 9-19, 8 Precision and Bias of the IDT Tester, 8 Theory of IDT Testing and Analysis, 11 Comparison of Compliance Values as Determined Using Uniaxial Tension, Uniaxial Compression, and the IDT Test, 17 25 CHAPTER 3 Interpretation, Appraisal, and Applications General Recommendations for Low-Temperature Creep and Strength Testing of Asphalt Concrete, 25 Coefficient of Thermal Contraction, 26 Estimating Creep Compliance and Strength Values, 26 Implementation, 27 AASHTO T322, 27 29 CHAPTER 4 Conclusions and Recommendations 30 REFERENCES A-1 APPENDIX A Review of AASHTO T322 and Recent Proposed Changes B-1 APPENDIX B Equipment Configurations for Creep and Strength Testing of Hot Mix Asphalt Concrete at Low Temperatures C-1 APPENDIX C Summary Data CONTENTS