Evaluation of the Moisture Susceptibility of WMA Technologies (2014)

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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 763 Evaluation of the Moisture Susceptibility of WMA Technologies Amy Epps Martin Edith Arambula Fan Yin Lorena Garcia Cucalon Arif Chowdhury Robert Lytton Jon Epps Cindy Estakhri Eun Sug Park Texas a&M TransporTaTion insTiTuTe The Texas a&M universiTy sysTeM College Station, TX Subscriber Categories Highways • Materials TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2014 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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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 research reported herein was performed under NCHRP Project 09-49 by the Texas A&M Transpor- tation Institute, a member of The Texas A&M University System. Dr. Amy Epps Martin, Professor of Civil Engineering at Texas A&M University and Research Engineer with the Texas A&M Transportation Insti- tute, served as the Principal Investigator; Ms. Cindy Estakhri, Senior Research Engineer at the Texas A&M Transportation Institute, served as the co-Principal Investigator. Other authors of this report included Dr. Edith Arambula, Fan Yin, Lorena Garcia Cucalon, Arif Chowdhury, Dr. Robert Lytton, Dr. Jon Epps, and Dr. Eun Sug Park, all of the Texas A&M Transportation Institute. Additional important contributors to this work from the Texas A&M Transportation Institute included Dr. David Newcomb, David Zeig, Rick Canatella, Stephen Walls, Stephen Johnson, Sarah Estakhri, Narain Hariharan, Aishwarya Baranikumar, Michael Blaylock, Joe Canatella, Mark Membreño, and Daniel Furdock. The research team gratefully acknowledges the cooperation and assistance provided by the agencies and contractors where field samples were collected, including the Iowa Department of Transportation and Norris Asphalt Paving Company, the Montana Department of Transportation and Jim Gillman Construc- tion, the Texas Department of Transportation and J.D. Ramming Paving Company, and the New Mexico Department of Transportation and James Hamilton Construction Company. In addition, the partner- ship with the Federal Highway Administration Mobile Asphalt Laboratory and other NCHRP warm mix asphalt projects was integral to this work and is greatly appreciated. CRP STAFF FOR NCHRP REPORT 763 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 09-49 PANEL Field of Bituminous Materials—Area of Materials and Construction Kim A. Willoughby, Washington State DOT, Olympia, WA (Chair) E. Ray Brown, Auburn, AL Ravi V. Chandran, Connecticut DOT, Rocky Hill, CT Matthew Corrigan, Federal Highway Administration, Washington, DC Dale S. Decker, Dale S. Decker, LLC, Eagle, CO Stacey D. Diefenderfer, Virginia Center for Transportation Innovation and Research, Charlottesville, VA Syed Waqar Haider, Michigan State University, East Lansing, MI James L. Horn, Alaska DOT and Public Facilities, Anchorage, AK Rita B. Leahy, California Asphalt Pavement Association, Sacramento, CA Scott A. Schram, Iowa DOT, Ames, IA Dean C. Weitzel, AMEC Environment & Infrastructure, Inc., Carson City, NV Jack H. Springer, FHWA Liaison Frederick Hejl, TRB Liaison

F O R E W O R D This report presents proposed guidelines for identifying potential moisture susceptibility in warm mix asphalt (WMA) and proposed revisions to the Appendix to AASHTO R 35, “Special Mixture Design Considerations and Methods for WMA” to implement the guide- lines. Thus, the report will be of immediate interest to materials engineers in state highway agencies and the asphalt pavement construction industry. Over the past decade, the use of WMA for asphalt pavement construction has dramatically increased in the United States. WMA is seen as an alternative to hot mix asphalt (HMA), which offers the potential to lower energy demand during production and construction, reduce emissions at the plant and the paver, and increase allowable haul distances. How- ever, questions remain about the long-term performance and durability of WMA pave- ments. One key issue is the moisture susceptibility of WMA pavements. Concerns about WMA moisture susceptibility include the possibility that aggregates will be inadequately dried at lower production temperatures and the fact that several WMA technologies intro- duce additional moisture in the production process. The objectives of NCHRP Project 9-49 were to (1) assess whether WMA technologies adversely affect the moisture susceptibility of asphalt pavements and (2) develop guidelines for identifying and limiting moisture susceptibility in WMA pavements. The research was performed by the Texas A&M Transportation Institute, College Station, Texas. The research was conducted through coordinated laboratory and field experiments that investigated the potential for moisture susceptibility in WMA compared to HMA. Design of the experiments was guided by a survey of the state DOTs and industry on WMA pavement construction and performance. The survey identified no instances of moisture damage to WMA pavements in service through 2010. This negative finding is supported by the results of recently completed NCHRP Project 9-47A, which conducted intensive evaluations of WMA pavements constructed across the United States between 2006 and 2011. Project 9-49 then focused on development of guidelines for WMA mix design and quality control to identify and minimize any possibility of moisture susceptibility. The laboratory experiments evaluated (1) laboratory-conditioning protocols for WMA before moisture- susceptibility testing, (2) the ability of standard test methods to detect moisture suscepti- bility of WMA, and (3) potential differences in WMA moisture susceptibility measured on laboratory-mixed and -compacted specimens; plant-mixed, laboratory-compacted speci- mens; and plant-mixed, field-compacted cores. The guidelines are presented in the form of a workflow of conditioning protocols and standard test methods that first assess the potential moisture susceptibility of a WMA mix design or field mixture and then recommend remedies to minimize such susceptibility. By Edward T. Harrigan Staff Officer Transportation Research Board

Specific test thresholds in the guidelines are based on the results of testing of WMA from field projects in Iowa, Montana, New Mexico, and Texas. This report fully documents the research and includes the following Appendixes: • Appendix A. Laboratory Conditioning Experiment • Appendix B. Moisture Conditioning Experiment • Appendix C. Performance Evolution Experiment • Appendix D. Construction Reports and Performance of Field Projects • Appendix E. Mixture Volumetrics • Appendix F. Proposed Draft Revisions to the Appendix to AASHTO R 35 • Appendix G. Future Work Plan to Evaluate Moisture Susceptibility of HMA and WMA • Appendix H. Statistical Results Appendix F is included herein. Appendixes A—E, G, and H are not provided herein but are available on the TRB website and can be found by searching for NCHRP Report 763.

C O N T E N T S 1 Summary 4 Chapter 1 Background 4 History and Definition 4 Benefits and Issues 5 Project Objectives and Scope 6 Relevant Literature and Survey Results 6 WMA Laboratory Conditioning 6 WMA Moisture Susceptibility 8 WMA Performance Evolution 10 Summary of National Survey and Interviews 16 Chapter 2 Research Approach 16 Field Projects 17 Iowa Field Project 19 Montana Field Project 19 Texas Field Project 20 New Mexico Field Project 20 Summary of Compaction Temperatures Used in the Field Projects 20 Laboratory Tests and Specimen Fabrication 20 Laboratory Tests 23 Specimen Fabrication 24 Experiment Designs 24 WMA Laboratory Conditioning 25 WMA Moisture Susceptibility 28 WMA Performance Evolution 31 Chapter 3 Findings and Applications 31 Mixture Volumetrics 31 WMA Laboratory Conditioning 34 WMA Moisture Susceptibility 34 Moisture Susceptibility 37 Effect of Anti-Stripping Agents 38 Effect of Specimen Type 39 WMA Performance Evolution 41 Phase I 42 Phase II 50 Revisions to Draft AASHTO Standards 51 Chapter 4 Findings, Discussion and Guidelines, and Suggested Research 51 Findings 51 WMA Laboratory Conditioning 51 WMA Moisture Susceptibility

52 WMA Performance Evolution 52 Performance Summary 54 Discussion and Guidelines 56 Suggested Research 60 References and Bibliography 65 Appendices A through E, G, and H F-1 Appendix F 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.

A B B R E V I A T I O N S , A C R O N Y M S , A N D I N I T I A L I S M S AADT Annual average daily traffic AFM Atomic force microscopy ANOVA Analysis of variance APA Asphalt pavement analyzer ASTM American Society for Testing and Materials AV Air voids BBS Bitumen Bond Strength DSR Dynamic shear rheometer ESAL Equivalent single axle loads FM Farm-to-market F/T Freeze-thaw FT Film thickness HMA Hot mix asphalt HSD Honestly Significant Differences HWTT Hamburg Wheel-Tracking Test IDT Indirect tensile LAS Liquid anti-stripping LCR Remaining life LEA Low emission/energy asphalt LMLC Laboratory-mixed laboratory-compacted LTOA Long-term oven aging LTPP Long-term pavement performance LVDT Linear variable differential transducers MIST Moisture-Induced Stress Tester NAPA National Asphalt Paving Association NCAT National Center for Asphalt Technology PG Performance grade PHT Pavement Health Track PMFC Plant-mixed field-compacted PMLC Plant-mixed plant-compacted QA Quality assurance QC Quality control RAP Reclaimed asphalt pavement RAS Recycled asphalt shingles RDT Repeated direct tension RSL Remaining Service Life SFE Surface Free Energy

SGC Superpave gyratory compactor SIP Stripping inflection point SMA Stone matrix asphalt SN Stripping number STOA Short-term oven aging TSR Tensile strength ratio TWG Technical Working Group TxDOT Texas Department of Transportation WMA Warm mix asphalt