Asphalt Binder Aging Methods to Accurately Reflect Mixture Aging (2021)

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2021 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 RESEARCH REPORT 967 Asphalt Binder Aging Methods to Accurately Reflect Mixture Aging Ramon Bonaquist AdvAnced AsphAlt technologies llc Kearneysville, WV Jeramie J. Adams Western reseArch institute Laramie, WY David A. Anderson State College, PA Subscriber Categories Materials • Pavements 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, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRB’s recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRB’s relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&I’s recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. 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Published research 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 by going to https://www.mytrb.org/MyTRB/Store/default.aspx Printed in the United States of America NCHRP RESEARCH REPORT 967 Project 09-61 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-67393-8 Library of Congress Control Number 2021935897 © 2021 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, FTA, GHSA, NHTSA, or TDC 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 research 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 National Academies of Sciences, Engineering, and Medicine. 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 Academies of Sciences, Engineering, and Medicine; the FHWA; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the Airport Cooperative Research Program do not endorse products or manufacturers. Trade or manufacturers’ names or logos appear herein solely because they are considered essential to the object of the report.

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.nationalacademies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Board’s varied activities annually engage about 8,000 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. Learn more about the Transportation Research Board at www.TRB.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 CRP STAFF FOR NCHRP RESEARCH REPORT 967 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Edward Harrigan, Senior Program Officer Anthony Avery, Program Associate Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications NCHRP PROJECT 09-61 PANEL Field of Materials and Construction—Bituminous Materials Darren G. Hazlett, University of Texas, Austin, Austin, TX (Chair) Cassady Allen, Florida Department of Transportation, Gainesville, FL Eric Biehl, Ohio Department of Transportation, Columbus, OH Emad Kassem, University of Idaho, Moscow, ID Derek J. Nener-Plante, FHWA, Sidney, ME Mansour Solaimanian, Pennsylvania State University, University Park, PA Jack S. Youtcheff, Jr., FHWA Liaison Nelson H. Gibson, TRB Liaison

This report will improve our ability to accurately condition asphalt binders to match their short- and long-term aging in asphalt mixtures. Thus, the report will be of immediate interest to engineers in state and local transportation agencies and in industry with respon- sibility for evaluating the performance of asphalt binders and mixtures. Asphalt binder ages during mixture production and throughout the service life of the pavement. This aging directly affects the stiffness and damage resistance of asphalt mix- tures. Current industry practice simulates short- and long-term aging of asphalt binders through conditioning with the rolling thin-film oven [AASHTO T 240, Standard Method of Test for Effect of Heat and Air on a Moving Film of Asphalt Binder (Rolling Thin- Film Oven Test)] and the pressurized aging vessel [AASHTO R 28, Standard Practice for Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel (PAV)], respectively. These methods and the parameters (e.g., temperature, pressure, and duration) involved in their use were developed for neat binders produced from conventional crude oil sources; they were adopted as standards primarily to aid performance grading of asphalt binders. Recently, there have been several significant changes in asphalt technology. The use of warm mix asphalt (WMA) and reclaimed asphalt pavement (RAP) has significantly increased, as has the use of additives and chemical and polymer modifiers to enhance binder proper- ties. The oxidation kinetics of binders in WMA, of mixtures containing RAP, or of binders containing additives and modifiers may be significantly different from that of conventional binders. A better understanding of binder aging and oxidation can improve our ability to predict and mitigate damage in asphalt pavements. Research to develop new or improved short- and long-term binder conditioning methods that reflect the aging of asphalt mixtures more accurately was warranted. Under NCHRP Project 09-61, “Short- and Long-Term Binder Aging Methods to Accu- rately Reflect Aging in Asphalt Mixtures,” Advanced Asphalt Technologies was tasked with developing practical laboratory aging methods to simulate more accurately the short-term (from production to placement) and long-term (in-service) aging of asphalt binders. The research conducted on short-term binder conditioning evaluated the acceptability of AASHTO T 240 as well as a PAV-based alternative to simulate short-term (from production to placement) binder aging. For long-term (in-service) binder conditioning, modifications to AASHTO R 28 as well as several innovative technologies were assessed. The key outcomes of this research are (1) Proposed Appendix X1 to AASHTO R 28, Modifications for 0.8 mm Thin Film Conditioning (12.5 g Binder Mass) and Commentary (Appendix A of the report) and (2) Proposed AASHTO Practice, 0.8 mm Static Film Short- and Long-Term Conditioning of Asphalt Binder and Commentary (Appendix B of the report). F O R E W O R D By Edward Harrigan Staff Officer Transportation Research Board

1 Summary 5 Chapter 1 Background 5 Problem 6 Objective and Scope 6 Organization 7 Chapter 2 Research Approach 7 Introduction 7 Considerations for Laboratory Conditioning 7 Quantity of Conditioned Binder for Grading 9 Target In-Service Pavement Age 11 Methods for Judging the Equivalency of Laboratory Conditioning and Field Aging 11 Short-Term Conditioned Binder 12 Long-Term Conditioned Binder 16 Binder Recovery 18 Evaluation of Short-Term Conditioning Procedures 18 Shortcomings of AASHTO T 240 18 Alternative Short-Term Conditioning Procedures 23 Assessment of Short-Term Conditioning Procedures 28 Evaluation of Long-Term Conditioning Procedures 28 Shortcomings of AASHTO R 28 30 Alternative Long-Term Conditioning Procedures 38 PAV Pan and Rack Design for Thinner Films 43 Selection of Procedures for Further Development 44 Short-Term Conditioning Selection Experiment 44 Objective 44 Experimental Design 45 Conditioning Procedures 48 Materials 49 Results and Analysis 64 PAV Operating Parameters Experiment 64 Objective 67 Experimental Design 71 Results and Analysis 106 Long-Term Conditioning Calibration Experiment 106 Objective 108 Experimental Design 115 Results and Analysis 150 Sensitivity Experiment 150 Objective 150 Experimental Design 151 Results and Analysis C O N T E N T S

155 Chapter 3 Findings and Application 155 Findings 155 Short-Term Conditioning 161 Long-Term Conditioning 162 Applications 162 Short-Term Conditioning 163 Long-Term Conditioning 164 Combined Short- and Long-Term Conditioning 166 Chapter 4 Conclusions and Recommendations 166 Conclusions 166 Short-Term Conditioning 167 Long-Term Conditioning 168 Proposals 168 Conditioning for Current Performance Grading 168 Conditioning for Adoption of DTC Criterion 169 Conditioning for Revised Performance Grading Criteria 169 Additional Research and Development 171 References A-1 Appendix A Proposed Appendix X1 to AASHTO R 28, Modifications for 0.8 mm Thin Film Conditioning (12.5 g Binder Mass) and Commentary B-1 Appendix B Proposed AASHTO Practice, 0.8 mm Static Film Short- and Long-Term Conditioning of Asphalt Binder and Commentary Note: Photographs, figures, and tables in this report may 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.