Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios (2020)

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2020 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 927 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios Amy Epps Martin Fawaz Kaseer Edith Arámbula-Mercado Akash Bajaj Lorena Garcia Cucalon Fan Yin Arif Chowdhury Jon Epps Charles Glover Elie Y. Hajj Nathan Morian Jo Sias Daniel Mirkat Oshone Reyhaneh Rahbar-Rastegar Chibuike Ogbo Gayle King Texas a&M TransporTaTion insTiTuTe The Texas a&M universiTy sysTeM College Station, TX Subscriber Categories Materials 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). 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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 927 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Anthony P. Avery, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications NCHRP PROJECT 09-58 PANEL Field of Materials and Construction—Area of Bituminous Materials James A. Musselman, Gainesville, FL (Chair) John C. Bartoszek, Payne & Dolan, Inc., Greenville, WI John A. D’Angelo, D’Angelo Consulting, LLC, Annandale, VA Joseph R. DeVol, Washington State DOT, Tumwater, WA Luke A. Johanneck, Minnesota DOT, Bemidji, MN Edmund Naras, Massachusetts DOT, Boston, MA Pedro Romero Zambrana, University of Utah, Salt Lake City, UT Victoria Woods-Bade, InVia Pavement Technologies, Vienna, MO Matthew Corrigan, FHWA Liaison Audrey Copeland, Industry Liaison ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 09–58, “The Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios” by the Texas A&M Transportation Institute (TTI), with the Texas A&M Sponsored Research Services serving as fiscal administrator. Dr. Amy Epps Martin, P.E., professor of civil engineering at Texas A&M University, was the principal investi- gator. Other authors of this report are Mr. Fawaz Kaseer, Dr. Edith Arámbula-Mercado, Mr. Akash Bajaj, Dr. Lorena Garcia Cucalon, Dr. Fan Yin, Mr. Arif Chowdhury, Dr. Jon Epps, Dr. Charles Glover, Dr. Elie Y. Hajj, Dr. Nathan Morian, Dr. Jo Sias Daniel, Dr. Mirkat Oshone, Mr. Chibuike Ogbo, and Dr. Gayle King. Thanks are also due to Mr. Thomas Henz, Ms. Katherine Klentzman, Mr. Kyle Doe, and Mr. Geoffrey Giannone at TTI for their work in generating laboratory results and to Dr. Dario Batioja- Alvarez, Ms. Sara Pournoman, Mr. Alberto Albejjani, Mr. Mateo Carvajal, Mr. Jhony Habbouche, and Mr. Murugaiyah Piratheepan at the University of Nevada, Reno, for their work in laboratory testing and analysis and materials sampling. The field projects required for the success of this study are realized based on the cooperation of state departments of transportation, contractors, and asphalt paving associa- tions; their participation is recognized and greatly appreciated. Donation of materials by recycling-agent manufacturers is also acknowledged.

NCHRP Research Report 927 presents an evaluation of how commercially available recycling agents affect the performance of asphalt mixtures incorporating reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS) at high recycled binder ratios. The report will be of immediate interest to materials engineers in state highway agencies and the construction industry with responsibility for design and production of asphalt paving mixtures. Economics, energy conservation, emission reduction, and conservation of natural resources have stimulated the expanding use of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt paving mixtures. RAS and RAP binders are very stiff and can create construction and performance issues. The use of relatively high percentages of stiff binders from RAP and RAS in an asphalt mixture can cause premature pavement dis- tress in the form of fatigue cracking, reflection cracking, low temperature cracking, accel- erated aging, and raveling. In addition, workability problems during placement can occur in cool weather conditions when asphalt mixtures with higher RAS and RAP contents are used. Uncertainty also exists about the ability of RAS and RAP binders to adequately blend with virgin asphalt binder at both hot and warm mix asphalt production temperatures. Asphalt paving mixtures with high RAP and RAS contents sometimes use virgin asphalt binders that are “softer” than the binder typically selected for the project’s climate and traffic. Alternatively, high RAP and RAS content mixtures may use recycling agents to “soften” or “rejuvenate” the stiff, oxidized RAP and RAS binders. These recycling agents include aro- matic extracts of crude oil, tall oils, vegetable oils, and reacted bio-based oils; all are com- mercial, proprietary products. While the use of such recycling agents reduces the stiffness of the resulting asphalt paving mixtures, the influence of these agents on specific aspects of asphalt mixture performance is not well understood. The objective of NCHRP Project 09–58 was to evaluate the effectiveness of recycling agents in asphalt mixtures with high RAS, RAP, or combined RAS/RAP binder ratios through a coordinated program of laboratory and field experiments. The research was performed by the Texas A&M Transportation Institute, Texas A&M University, College Station, Texas, in association with the University of Nevada, Reno, Nevada; the University of New Hampshire, Durham, New Hampshire; and Dr. Gayle King, Consultant, Houston, Texas. The research involved an extensive program of laboratory experiments drawing on binders, mortars, and mixtures from field construction projects in Texas, Nevada, Indiana, Wisconsin, and Delaware. These materials were tested to develop and validate the following: material selection guidelines for base binders, recycled materials, and recycling agents; a recycling agent dose selection method; material proportioning strategies; RAP binder availability F O R E W O R D By Edward Harrigan Staff Officer Transportation Research Board

factors; and binder blend and mixture evaluation tools including aging protocols, recycling agent blending methods, and laboratory performance tests and proposed thresholds to control cracking and rutting resistance of asphalt mixtures with high recycled binder ratios. The results of these experiments were analyzed to develop a proposed AASHTO Standard Practice for the informed use of recycled agents, especially in asphalt mixtures with recycled binder ratios in the range of from 0.3 to 0.5. The key outcome of this research is the proposed AASHTO Standard Practice (Appen- dix I) for the use of recycling agents in asphalt mixtures incorporating RAP and RAS for con- sideration and possible adoption by the AASHTO Committee on Materials and Pavements. The practice provides tools based on standard test methods for selecting and proportioning recycling agents and evaluating the performance characteristics of the rejuvenated binder and mixtures.

1 Summary 4 Chapter 1 Introduction 5 1.1 Project Overview and Objectives 13 1.2 Key Results from Phase 1 15 1.3 Recent Relevant Literature 15 1.4 Scope of Final Report 20 1.5 Experiment Design 36 Chapter 2 Key Results from Phase 2 36 2.1 Development of Recycling-Agent Dose Selection Method 47 2.2 Chemical Compatibility of Binder Blends 51 2.3 Rheological Balance of Binder Blends 54 2.4 Representative Binder Blending 64 2.5 Mixture Cracking Resistance by S-VECD 68 2.6 Comparison of Specimen Types 70 2.7 Key Findings 71 Chapter 3 Field and Laboratory Performance of High RBR Mixtures 71 3.1 Pavement Distress Summary 71 3.2 Field Core Results 76 3.3 Comparison of Laboratory Results and Field Performance 78 3.4 Key Findings 79 Chapter 4 Expanded Laboratory Performance of High RBR Binder Blends and Mixtures 79 4.1 Binder Blend Rheology with Aging 85 4.2 Binder Blend Aging Prediction 94 4.3 Recycling-Agent Characterization 103 4.4 Mixture Performance 116 4.5 Recycled Binder Availability 125 4.6 Key Findings 127 Chapter 5 Practical Tools for Evaluation of High RBR Binder Blends and Mixtures 127 5.1 Component Materials Selection Guidelines 132 5.2 Recycling-Agent Dose Selection Method 133 5.3 Materials Proportioning Guidance 135 5.4 Binder Blend Rheological Evaluation Tools 135 5.5 Mixture Performance Evaluation Tools 138 5.6 RAP Recycled Binder Availability Factor 138 5.7 Laboratory Aging and Climate Effects 144 5.8 Key Findings C O N T E N T S

145 Chapter 6 Summary and Path Forward 145 6.1 Summary 146 6.2 Path Forward 151 References 157 Abbreviations and Symbols A-1 Appendix A Texas Construction Report B-1 Appendix B Nevada Construction Report C-1 Appendix C Indiana Construction Report D-1 Appendix D Wisconsin Construction Report E-1 Appendix E Delaware Construction Report F-1 Appendix F Binder Blend Aging Prediction Data G-1 Appendix G Recycling Agent Characterization Data H-1 Appendix H Economics Associated with the Use of Recycling Agents I-1 Appendix I Draft AASHTO Standard Practice 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.