Specifying and Measuring Asphalt Pavement Density to Ensure Pavement Performance (2017)

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2017 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 856 Specifying and Measuring Asphalt Pavement Density to Ensure Pavement Performance Dale S. Decker Dale S. Decker, llc Eagle, Colorado Subscriber Categories Construction  •  Materials  •  Pavements 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). 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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 National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway 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 National Academies. 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Published research 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 RESEARCH REPORT 856 Project 20-07/Task 382 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-44650-1 Library of Congress Control Number 2017947967 © 2017 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 research 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. Marcia McNutt 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 National 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 AUTHOR ACKNOWLEDGMENTS The author acknowledges the members of the AASHTO Subcommittees on Materials and Construc- tion for their support of this project. Additionally, appreciation goes to the members of the National Asphalt Pavement Association, state asphalt pavement associations, and the provincial Ministries of Transportation in Canada for their participation in the survey. CRP STAFF FOR NCHRP RESEARCH REPORT 856 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 Sreyashi Roy, Editor NCHRP PROjECT 20-07/TASK 382 PANEL Field of Special Projects Christopher D. Abadie, Pine Bluff Sand and Gravel Company, Baton Rouge, LA Peter C. Capon, Rieth-Riley Construction, Inc., Goshen, IN Audrey Copeland, National Asphalt Pavement Association, Lanham, MD John E. Grieco, Massachusetts DOT, Hopkinton, MA Chad Hawkins, South Carolina DOT, Columbia, SC Robert E. Lee, Texas DOT, Austin, TX Ross Metcalfe, Montana DOT, Helena, MT Brett Stanton, Superior Bowen, Kansas City, MO Timothy B. Aschenbrener, FHWA Liaison

This report presents a critical analysis of the current state of knowledge and existing agency practices to measure and specify the in-place density of asphalt pavements. The report will be of immediate interest to engineers in state highway agencies and industry with responsibility for design, construction, and quality assurance of asphalt pavements. In the mid-1990s, the Strategic Highway Research Program developed the Superpave mix design method to provide the state highway agencies with the opportunity to standardize key asphalt binder and mixture test methods and specifications. These methods and specifications have played a key role in the substantial improvement of asphalt pavement performance over the past 20 years. However, there is a continuing recognition that the level of in-place density (also expressed as air voids content) attained by mixture compaction during construction also plays a major role in achieving satisfactory long-term performance. Too high a density can leave a pavement prone to rutting and shoving while too low a density can contribute to cracking, moisture damage, and raveling. At present, there is no standard on how agencies should measure and set criteria for in-place pavement density. Most agencies have developed their own methodologies and acceptance criteria based on past practices and experiences. The result is that widespread variability exists nationally with regard to the methods of measuring in-place density, test locations in a paving lane, frequency of tests, specified density levels, as well as how mea- sured data are applied against the specified minimum acceptance criteria. This is in stark contrast to the standardization of key asphalt mixture and binder properties and test methods through the Superpave mix design method. The objective of NCHRP Project 20-07/Task 382 was to determine the current state of knowledge and existing agency practices to measure and specify the in-place density of asphalt pavements. NCHRP Research Report 856 represents a critical analysis of this information intended to guide agency decisions on selecting measurement methods and requirements for in-place density and to identify the specific knowledge gaps that need to be addressed to provide a complete basis for establishing more comprehensive density standards. The research was conducted by Dale S. Decker, LLC, Eagle, Colorado. This report is supported by a survey, “Summary of Agency Survey Responses,” which is available for download from the project webpage at http://apps.trb.org/cmsfeed/ TRBNetProjectDisplay.asp?ProjectID=3997. F O R E W O R D By Edward T. Harrigan Staff Officer Transportation Research Board

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. 1  Summary 3 Chapter 1 Introduction 3 Literature Review 4 Survey 6 Chapter 2 Survey to Determine the Density  of Asphalt Pavements 6 General Issues in the Density of Asphalt Pavements 11 Specification Types for the Control of Density 22 Density Measurement Techniques 31 Construction Parameters Affecting Density 41 Longitudinal Joint Construction 45 Emerging Technologies for Achieving Density 49 Chapter 3 Findings 49 General Issues in the Density of Asphalt Pavements 49 Specification Types for the Control of Density 50 Density Measurement Techniques 51 Construction Parameters Affecting Density 51 Longitudinal Joint Construction 51 Emerging Technologies for Achieving Density 52 Chapter 4 Conclusions 53  Bibliography C O N T E N T S