Precision of the Dynamic Modulus and Flow Number Tests Conducted with the Asphalt Mixture Performance Tester (2011)

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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2011 www.TRB.org 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 702 Subscriber Categories Highways and Materials Precision of the Dynamic Modulus and Flow Number Tests Conducted with the Asphalt Mixture Performance Tester Ramon Bonaquist ADVANCED ASPHALT TECHNOLOGIES, LLC Sterling, VA Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

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CRP STAFF FOR NCHRP REPORT 702 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Melanie Adcock, Senior Program Assistant Eileen P. Delaney, Director of Publications Doug English, Editor NCHRP PROJECT 9-29 PANEL Field of Materials and Construction—Area of Bituminous Materials Larry L. Michael, Hagerstown, MD (Chair) Gary A. Frederick, New York State DOT, Albany, NY Cindy LaFleur, Oldcastle Materials, Albany, NY Dean A. Maurer, Practical Asphalt Solutions Technology, Lewisberry, PA Leslie Ann McCarthy, Villanova University, Villanova, PA Murari M. Pradhan, Arizona DOT, Phoenix, AZ John J. Weigel, Jr., Cinack Solutions LLC, Pewaukee, WI Thomas Harman, FHWA Liaison Audrey Copeland, Turner Fairbank Highway Research Center Liaison John D’Angelo, D’Angelo Consulting, LLC Liaison Frederick Hejl, TRB Liaison AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 9-29 by Advanced Asphalt Tech- nologies, LLC. Ramon Bonaquist, Chief Operating Officer for Advanced Asphalt Technologies, LLC, served as Principal Investigator for the project and was the primary author of this report. Donald W. Christensen, Senior Engineer for Advanced Asphalt Technologies, LLC, assisted with the design of the interlaboratory study. Laboratories at the following organizations participated in the study: • Advanced Asphalt Technologies, LLC • Asphalt Institute • Dongre Laboratory Services, Inc. • Federal Highway Administration • Florida Department of Transportation • Mathy Technology and Engineering Services, Inc. • National Center for Asphalt Technologies • Utah Department of Transportation 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

NCHRP Report 702: Precision of the Dynamic Modulus and Flow Number Tests Conducted with the Asphalt Mixture Performance Tester describes the development of precision state- ments for the dynamic modulus and flow number tests conducted with the Asphalt Mixture Performance Tester (AMPT). Thus, the report will be of particular interest to materials and pavement structural design engineers in state highway agencies, as well as to materials suppliers and paving contractors. The present hot-mix asphalt (HMA) volumetric mix design method used by the major- ity of state highway agencies was developed in the asphalt component of the Strategic High- way Research Program (1987–1993). This method—standardized as AASHTO M 323 and R 35—does not include a simple, mechanical “proof” test analogous to the Marshall stabil- ity and flow tests or the Hveem stabilometer method. Though the utility and soundness of the HMA mix design method are evident by its almost ubiquitous, present-day use, mix designers from the beginning have asked for com- plementary performance tests to quickly and easily proof-test candidate mix designs. Work sponsored by FHWA and then NCHRP in the period 1996–2006 (and reported in NCHRP Reports 465, 547, and 580) recommended three test and parameter combinations as perfor- mance tests for permanent deformation: (1) the dynamic modulus, E*, determined with the triaxial dynamic modulus test; (2) the flow number, Fn, determined with the triaxial repeated load test; and (3) the flow time, FT, determined with the triaxial static creep test. The dynamic modulus, E*, also was chosen as the simple performance test for fatigue crack- ing as well as the chief HMA materials characterization test for HMA pavement design with the Mechanistic-Empirical Pavement Design Guide (MEPDG). Under NCHRP Project 9-29, “Simple Performance Tester for Superpave Mix Design,” Advanced Asphalt Technologies, LLC, was assigned the task of designing, procuring, and evaluating the AMPT for testing HMA mixtures for (1) permanent deformation and fatigue cracking in HMA mix design and (2) materials characterization for pavement structural design with the MEPDG. In the portion of NCHRP Project 9-29 reported here (Phase VI), the research team con- ducted an interlaboratory study to prepare precision statements for the dynamic modulus and flow number tests carried out according to AASHTO TP 79, “Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Asphalt Mixture Per- formance Tester (AMPT).” The interlaboratory study was designed, conducted, and ana- lyzed in accordance with ASTM Standard Practice E691, “Conducting an Interlaboratory Study to Determine the Precision of a Test Method.” F O R E W O R D By Edward T. Harrigan Staff Officer Transportation Research Board

The interlaboratory study produced precision statements for (1) dynamic modulus and phase angle, (2) unconfined flow number for the NCHRP Project 9-33 testing conditions, and (3) permanent strain in confined flow number tests using the NCHRP Project 9-30A testing conditions. These precision statements are in the form of tables proposed for addi- tion to AASHTO TP 79, subject to their review and acceptance by the AASHTO Highway Subcommittee on Materials. This report presents the full text of the contractor’s final report for Phase VI and the fol- lowing nine appendices: Appendix A: Interlaboratory Study Instructions Appendix B: Loose Mix Dynamic Modulus Test Data Appendix C: Prefabricated Core Dynamic Modulus Test Data Appendix D: Loose Mix Dynamic Modulus Statistical Analysis Appendix E: Prefabricated Core Dynamic Modulus Statistical Analysis Appendix F: Unconfined Flow Number Test Data Appendix G: Unconfined Flow Number Statistical Analysis Appendix H: Confined Flow Number Test Data Appendix I: Confined Flow Number Statistical Analysis Earlier work completed in Phases I through V is presented in NCHRP Reports 513, 530, 614, and 629.

C O N T E N T S 1 Summary 3 Chapter 1 Introduction and Research Approach 3 1.1 Problem and Purpose 3 1.2 Scope 4 1.3 Experimental Design and Analysis 4 1.3.1 Experimental Design 6 1.3.2 Analysis 9 Chapter 2 Results and Analysis 9 2.1 Dynamic Modulus Test 9 2.1.1 Tests on Loose Mix Specimens 12 2.1.2 Tests on Prefabricated Cores 19 2.1.3 Comparison of Loose Mix and Prefabricated Core Data 21 2.1.4 Final Repeatability and Reproducibility Statistics 23 2.1.5 Precision Statements 26 2.2 Unconfined Flow Number 26 2.2.1 Tests on Loose Mix Specimens 27 2.2.2 Tests on Prefabricated Cores 29 2.2.3 Comparison of Loose Mix and Prefabricated Core Data 30 2.2.4 Precision Statements 30 2.3 Confined Flow Number 31 2.3.1 Tests on Loose Mix Specimens 32 2.3.2 Tests on Prefabricated Cores 34 2.3.3 Comparison of Loose Mix and Prefabricated Core Data 35 2.3.4 Precision Statements 36 2.4 Specimen Fabrication Effects 36 2.4.1 Compactor Type 37 2.4.2 Air Voids 37 2.4.3 Specimen Age 40 Chapter 3 Conclusions and Recommendations 40 3.1 Conclusions 40 3.1.1 Dynamic Modulus Test 40 3.1.2 Unconfined Flow Number Test 42 3.1.3 Confined Flow Number Test 42 3.1.4 Specimen Fabrication Effects 42 3.2 Recommendations 44 References 45 Appendix A Interlaboratory Study Instructions 49 Appendix B Loose Mix Dynamic Modulus Test Data

98 Appendix C Prefabricated Core Dynamic Modulus Test Data 147 Appendix D Loose Mix Dynamic Modulus Statistical Analysis 164 Appendix E Prefabricated Core Dynamic Modulus Statistical Analysis 181 Appendix F Unconfined Flow Number Test Data 182 Appendix G Unconfined Flow Number Statistical Analysis 186 Appendix H Confined Flow Number Test Data 189 Appendix I Confined Flow Number Statistical Analysis