Comparing the Volumetric and Mechanical Properties of Laboratory and Field Specimens of Asphalt Concrete (2016)

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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 818 Comparing the Volumetric and Mechanical Properties of Laboratory and Field Specimens of Asphalt Concrete Louay N. Mohammad Mostafa A. Elseifi Samuel B. Cooper, III Louisiana TransporTaTion research cenTer Louisiana sTaTe universiTy Baton Rouge, LA C. S. Hughes Charlottesville, VA Joe W. Button College Station, TX Ervin L. Dukatz, Jr. MTe services, inc. Onalaska, WI Subscriber Categories Construction • Materials • Pavements TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2016 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 is the most effective way to solve 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 results in increasingly complex problems of wide inter- est to highway 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, United States Department of Transportation. 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 Academies is an insurance of objectivity; and TRB maintains a full-time staff of specialists in high- way 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 identified by chief administrators and other staff of the highway and transporta- tion departments and by committees of AASHTO. Topics of the highest merit are selected by the AASHTO Standing Committee on Research (SCOR), and each year SCOR’s recommendations are proposed to the AASHTO Board of Directors and the Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the Acad- emies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement, rather than to substitute for or duplicate, other highway research programs. Published 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 http://www.national-academies.org and then searching for TRB Printed in the United States of America NCHRP REPORT 818 Project 09-48 ISSN 0077-5614 ISBN 978-0-309-37508-5 Library of Congress Control Number 2016933709 © 2016 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, FMCSA, FRA, FTA, Office of the Assistant Secretary for Research and Technology, PHMSA, 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 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; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; 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.

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. Ralph J. Cicerone 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. C. D. Mote, Jr., 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 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.national-academies.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 increase the benefits that transportation contributes to society by providing leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Board’s varied committees, task forces, and panels annually engage about 7,000 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 REPORT 818 Christopher W. Jenks, Director, Cooperative Research Programs Christopher Hedges, Manager, National Cooperative Highway Research Program Edward T. Harrigan, Senior Program Officer Anthony Avery, Senior Program Assistant Eileen P. Delaney, Director of Publications Hilary Freer, Senior Editor NCHRP PROJECT 09-48 PANEL Field of Materials and Construction—Area of Bituminous Materials Rita B. Leahy, California Asphalt Pavement Association, Sacramento, CA (Chair) John A. D’Angelo, D’Angelo Consulting, LLC, Annandale, VA Jon A. Epps, Texas A&M Transportation Institute, College Station, TX Kee Y. Foo, California DOT, Sacramento, CA Larry L. Michael, LLM Asphalt Technology Consulting, Hagerstown, MD Allen H. Myers, Kentucky Transportation Cabinet, Frankfort, KY Gregory A. Sholar, Florida DOT, Gainesville, FL Haifang Wen, Washington State University, Pullman, WA James M. Winford, Jr., Prairie Contractors, Inc., Opelousas, LA Zhanping You, Michigan Technological University, Houghton, MI John Bukowski, FHWA Liaison Eric J. Weaver, FHWA Liaison

F O R E W O R D By Edward T. Harrigan Staff Officer Transportation Research Board This report presents a proposed practice for evaluating the cause and magnitude of vari- ability of specimen types tested in quality control and/or assurance programs for asphalt paving projects. Thus, the report will be of immediate interest to engineers in state highway agencies and the construction industry with responsibility for testing asphalt mixtures and conducting quality control and/or assurance programs. Many transportation agencies conduct quality assurance (QA) programs on asphalt paving projects. QA requires the contractor and the owner agency to share testing responsibilities. Typically, the contractor conducts the majority of the testing for quality control and accep- tance purposes, and the agency conducts fewer tests to verify the contractor’s test results. Test- ing may measure both volumetric properties, such as air voids (Va), voids in mineral aggregate (VMA), and asphalt content, and mechanical properties such as loaded-wheel test (LWT) rut depth, indirect tensile test (IDT) strength, and dynamic modulus (E*). The results of QA testing conducted by the agency and the contractor are often compared statistically to verify the contractor’s test results. Such comparisons help the agency judge whether its QA test results are from the same population as the contractor’s test results. However, because the tests are performed by different operators using different equipment and with potentially different methods, variability of the test results is inevitable. A further source of variability arises when results from laboratory-mixed and compacted (LL) specimens are compared to those from plant-mixed, laboratory-compacted (PL) speci- mens, or plant-mixed, field-compacted (PF) specimens, or both, on a single project. A major barrier to conducting a sound QA program is quantifying the variability that arises when it is necessary to compare the properties of asphalt mixture specimens that may be (1) produced in a laboratory or at the plant, (2) compacted in different physical locations, and (3) compacted in the laboratory or in-place on the pavement. The objectives of this research were to (1) determine causes of variability and tolerances for volumetric and mechanical properties of dense-graded asphalt mixtures measured within and among the three specimen types; and (2) propose a practice for state DOTs to incor- porate these results in specifications and criteria for (a) quality assurance, (b) mix design verification or validation, and (c) structural design and forensic studies. The research was conducted by the Louisiana Transportation Research Center, Louisiana State University, Baton Rouge, Louisiana, and supported by MTE Services, Inc., Onalaska, Wisconsin. The research was conducted in two phases. In Phase I, datasets of laboratory and field test data were collected and pooled in a meta-analysis in an attempt to determine (1) levels of variability in asphalt mixtures and (2) the factors causing variability among and between the three specimen types. Despite the inclusion of 25 extensive datasets representing roughly

8,000 individual mixtures in the meta-analysis, the results of the analysis were inconclusive. Phase II was then undertaken—a program testing LL, PL, and PF specimens from paving projects across the United States to quantify the effects of process-based factors on the vari- ability of volumetric and mechanical properties of the specimen types. The key outcome of the research is a proposed practice in Chapter 6 for evaluating the cause and magnitude of variability within and among the three specimen types. In addition, toler- ances of volumetric and conversion factors between the three specimen types of mechanical properties evaluated are proposed based on the average difference between specimen com- parisons for the mixtures evaluated in Phase II. Agencies may use these proposed values to evaluate and adjust their current tolerances, as discussed in Chapters 6 and 7. This report fully documents the research. Four appendixes are available to download from the NCHRP Project 09-48 web page at http://apps.trb.org/cmsfeed/TRBNetProjectDisplay .asp?ProjectID=2503: • Appendix A Literature Review • Appendix B Phase I Preliminary Research Meta-Analysis • Appendix C Individual Mixture Analysis • Appendix D Job Mix Formulae

C O N T E N T S 1 Summary 3 Chapter 1 Introduction 3 1.1 Asphalt Mixture Design 3 1.2 Asphalt Mixture Production 3 1.3 QA Testing 3 1.4 Problem Statement 4 1.5 Objectives and Scope 4 1.6 Research Method 4 1.7 Report Outline 6 Chapter 2 Phases I and IA 6 2.1 Phase I: Levels of Variability in Volumetric and Mechanical Properties of Asphalt Mixtures 6 2.2 Phase IA: Factors Causing Variability Between Specimen Types 18 2.3 Meta-Analysis 22 2.4 Conclusions and Findings of Phase IA 24 Chapter 3 Experimental Program 24 3.1 Determine Process-Based Factors 24 3.2 Mixture Evaluation 24 3.3 Test Factorial Design 26 3.4 Mixture Descriptions 28 Chapter 4 Method 28 4.1 Description of Specimen Preparation 30 4.2 Volumetric Tests 31 4.3 Mechanical Tests 32 4.4 Statistical Analyses 35 4.5 Delta Analyses 35 4.6 Pavement Performance Prediction 38 4.7 Development of Specification Recommendations 39 Chapter 5 Results and Discussion 39 5.1 Individual Mixture Analyses 52 5.2 Combined Statistical Analysis 60 Chapter 6 Proposed Guidelines for Recommended Practice 60 6.1 Specification Recommendations 64 6.2 Effect of Variability on Performance

68 Chapter 7 Implementation Recommendations 68 7.1 Effect of Process-Based Factors 68 7.2 Volumetric Properties Tolerance Recommendation 68 7.3 Conversion of Mechanical Properties Among Specimen Types 71 Chapter 8 Summary and Conclusions 71 8.1 Effect of Process-Based Factors 72 8.2 Proposed Tolerances 72 8.3 Mechanical Conversion Among Specimen Types 72 8.4 Effect of Specimen Type on Pavement Performance Prediction 73 References and Bibliography 76 Abbreviations and Acronyms 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.