Improved Mix Design, Evaluation, and Materials Management Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content (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 752 Improved Mix Design, Evaluation, and Materials Management Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content Randy West James Richard Willis NatioNal CeNter for asphalt teChNology auburN uNiversity Auburn, AL Mihai Marasteanu DepartmeNt of Civil eNgiNeeriNg uNiversity of miNNesota Minneapolis, MN Subscriber Categories Highways • Construction • 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. 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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.

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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 REPORT 752 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Anthony P. Avery, Senior Program Assistant Eileen P. Delaney, Director of Publications Hilary Freer, Senior Editor NCHRP PROJECT 09-46 PANEL Field of Materials and Construction—Area of Bituminous Materials James A. Musselman, Florida DOT, Gainesville, FL (Chair) John D’Angelo, D’Angelo Consulting, LLC, Annandale, VA Sheila Hines, Georgia DOT, Forest Park, GA Daniel P. Johnston, Pierre, SD Dean A. Maurer, Practical Asphalt Solutions Technology, Lewisberry, PA Murari M. Pradhan, Arizona DOT, Phoenix, AZ John J. Weigel, Jr., Cinack Solutions, LLC, Pewaukee, WI Nelson H. Gibson, FHWA Liaison Audrey Copeland, National Asphalt Pavement Association Liaison Frederick Hejl, TRB Liaison

F O R E W O R D By Edward T. Harrigan Staff Officer Transportation Research Board This report describes proposed revisions to AASHTO R 35, Superpave Volumetric Design for Hot Mix Asphalt (HMA), and AASHTO M 323, Superpave Volumetric Mix Design, to accommodate the design of asphalt mixtures with high reclaimed asphalt pavement (RAP) contents. Thus, the report will be of immediate interest to materials engineers in state highway agencies and industry with responsibility for the design and evaluation of asphalt mixtures. NCHRP Project 9-46, “Improved Mix Design, Evaluation, and Materials Management Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content,” was con- ducted by the National Center for Asphalt Technology, Auburn, Alabama, with participa- tion by the University of Minnesota, Minneapolis, Minnesota. The objectives of the project were to (1) develop a mix design and evaluation procedure that provides satisfactory long-term performance for asphalt mixtures containing high RAP contents—in the range of 25 to 50 percent or greater—and (2) propose changes to existing AASHTO standards to adapt them to the design of high RAP content mixtures. The project team conducted a comprehensive laboratory experiment to answer basic questions about preparing and characterizing RAP materials for mix designs. A series of mix designs was then prepared with materials from four different parts of the United States with different RAP contents and different virgin binders. Those mix designs were evaluated against standard Superpave criteria and a set of performance-related tests to further assess the mix designs for their susceptibility to common forms of distress, particularly fatigue cracking, low-temperature cracking, and moisture damage. A concurrent effort developed a set of best practices for RAP management in field production and construction from infor- mation obtained through a literature review, surveys of current practices in the industry, discussions with numerous contractor QC personnel, and analysis of contractor stockpile QC data from across the United States The research found that only minor, though important, revisions to the current AASHTO standards for asphalt mix design, AASHTO R 35 and M 323, were needed to adapt them for the successful design of high RAP content asphalt mixtures. As expected, high RAP contents substantially increased the dynamic modulus of the asphalt mixtures as well as their rutting resistance as measured by the confined flow number test. Tensile strength ratios of high RAP content mixtures as measured by AASHTO T 283 were comparable to those of control mixtures without RAP, indicating similar moisture damage susceptibilities. As might be expected, compared to control mixtures without RAP, the high RAP content mixtures generally had lower fracture energies at test temperatures used to evaluate suscep- tibility to fatigue and low-temperature cracking. This finding suggests that careful attention

should be given to the selection of the performance grade of the virgin binder used in high RAP content mixtures to minimize any long-term risk of cracking distress. The contractor’s final report fully documents the research and includes Appendix A, which is not provided herein but is available on the TRB website and can be found by searching for NCHRP Report 752. Appendixes B through D are included herein as well as on the website as part of NCHRP Report 752.

C O N T E N T S 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. 1 Summary 5 Chapter 1 Background 5 Introduction 5 Project Objectives 5 Literature Review 28 Chapter 2 Research Plan 28 Part II: Preliminary Experiments 29 Part III: High RAP Content Mix Design and Performance Testing 42 Chapter 3 Results and Analyses 42 RAP Drying Experiment 42 RAP Heating Experiment 43 RAP Aggregate Specific Gravity Experiment 44 Volumetric Properties of the Mix Designs 48 Effect of Binder Grade and Binder Source 51 Estimated Effective Binder Grades 52 Dynamic Modulus Results 58 Effects of Mix Design Factors on Dynamic Modulus 60 Backcalculated Effective Binder Grade from Dynamic Modulus Tests 65 Moisture Damage Susceptibility Results 68 Flow Number Results 70 Statistical Analysis of Flow Number Results 71 Summary of Flow Number Results 71 Fatigue Cracking 74 Low-Temperature Cracking 92 Chapter 4 Findings 92 RAP Management 92 Characterizing RAP Materials for Mix Design 94 Field Performance of High RAP Content Mixes 94 Mix Designs Using High RAP Contents 95 Proposed Recommendations 98 References 101 Appendix A Draft Standard for Semi-Circular Bend Test 102 Appendix B Proposed Standard Practice for Superpave Volumetric Design for Hot Mix Asphalt 120 Appendix C Proposed Standard Specification for Superpave Volumetric Mix Design 132 Appendix D Best Practices for RAP Management