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NCHRP NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM REPORT 712 Optimization of Tack Coat for HMA Placement

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TRANSPORTATION RESEARCH BOARD 2012 EXECUTIVE COMMITTEE* OFFICERS Chair: Sandra Rosenbloom, Professor of Planning, University of Arizona, Tucson Vice Chair: Deborah H. Butler, Executive Vice President, Planning, and CIO, Norfolk Southern Corporation, Norfolk, VA Executive Director: Robert E. Skinner, Jr., Transportation Research Board MEMBERS J. Barry Barker, Executive Director, Transit Authority of River City, Louisville, KY William A.V. Clark, Professor of Geography and Professor of Statistics, Department of Geography, University of California, Los Angeles Eugene A. Conti, Jr., Secretary of Transportation, North Carolina DOT, Raleigh James M. Crites, Executive Vice President of Operations, Dallas-Fort Worth International Airport, TX Paula J. C. Hammond, Secretary, Washington State DOT, Olympia Michael W. Hancock, Secretary, Kentucky Transportation Cabinet, Frankfort Chris T. Hendrickson, Duquesne Light Professor of Engineering, Carnegie-Mellon University, Pittsburgh, PA Adib K. Kanafani, Professor of the Graduate School, University of California, Berkeley Gary P. LaGrange, President and CEO, Port of New Orleans, LA Michael P. Lewis, Director, Rhode Island DOT, Providence Susan Martinovich, Director, Nevada DOT, Carson City Joan McDonald, Commissioner, New York State DOT, Albany Michael R. Morris, Director of Transportation, North Central Texas Council of Governments, Arlington Neil J. Pedersen, Consultant, Silver Spring, MD Tracy L. Rosser, Vice President, Regional General Manager, Wal-Mart Stores, Inc., Mandeville, LA Henry G. (Gerry) Schwartz, Jr., Chairman (retired), Jacobs/Sverdrup Civil, Inc., St. Louis, MO Beverly A. Scott, General Manager and CEO, Metropolitan Atlanta Rapid Transit Authority, Atlanta, GA David Seltzer, Principal, Mercator Advisors LLC, Philadelphia, PA Kumares C. Sinha, Olson Distinguished Professor of Civil Engineering, Purdue University, West Lafayette, IN Thomas K. Sorel, Commissioner, Minnesota DOT, St. Paul Daniel Sperling, Professor of Civil Engineering and Environmental Science and Policy; Director, Institute of Transportation Studies; and Acting Director, Energy Efficiency Center, University of California, Davis Kirk T. Steudle, Director, Michigan DOT, Lansing Douglas W. Stotlar, President and CEO, Con-Way, Inc., Ann Arbor, MI C. Michael Walton, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin EX OFFICIO MEMBERS Rebecca M. Brewster, President and COO, American Transportation Research Institute, Smyrna, GA Anne S. Ferro, Administrator, Federal Motor Carrier Safety Administration, U.S.DOT LeRoy Gishi, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Washington, DC John T. Gray II, Senior Vice President, Policy and Economics, Association of American Railroads, Washington, DC John C. Horsley, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC Michael P. Huerta, Acting Administrator, Federal Aviation Administration, U.S.DOT David T. Matsuda, Administrator, Maritime Administration, U.S.DOT Michael P. Melaniphy, President and CEO, American Public Transportation Association, Washington, DC Victor M. Mendez, Administrator, Federal Highway Administration, U.S.DOT Tara O'Toole, Under Secretary for Science and Technology, U.S. Department of Homeland Security, Washington, DC Robert J. Papp (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, U.S. Department of Homeland Security, Washington, DC Cynthia L. Quarterman, Administrator, Pipeline and Hazardous Materials Safety Administration, U.S.DOT Peter M. Rogoff, Administrator, Federal Transit Administration, U.S.DOT David L. Strickland, Administrator, National Highway Traffic Safety Administration, U.S.DOT Joseph C. Szabo, Administrator, Federal Railroad Administration, U.S.DOT Polly Trottenberg, Assistant Secretary for Transportation Policy, U.S.DOT Robert L. Van Antwerp (Lt. Gen., U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers, Washington, DC Barry R. Wallerstein, Executive Officer, South Coast Air Quality Management District, Diamond Bar, CA Gregory D. Winfree, Acting Administrator, Research and Innovative Technology Administration, U.S.DOT *Membership as of February 2012.

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N AT I O N A L C O O P E R AT I V E H I G H W AY R E S E A R C H P R O G R A M NCHRP REPORT 712 Optimization of Tack Coat for HMA Placement Louay N. Mohammad Mostafa A. Elseifi Abraham Bae Nachiketa Patel Louisiana Transportation Research Center Louisiana State University Baton Rouge, LA Joe Button Texas A&M University College Station, TX James A. Scherocman Cincinnati, OH Subscriber Categories Highways Materials Construction Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration TRANSPORTATION RESEARCH BOARD WASHINGTON, D.C. 2012 www.TRB.org

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NATIONAL COOPERATIVE HIGHWAY NCHRPREPORT 712 RESEARCH PROGRAM Systematic, well-designed research provides the most effective Project 09-40 approach to the solution of many problems facing highway ISSN 0077-5614 administrators and engineers. Often, highway problems are of local ISBN 978-0-309-21397-4 interest and can best be studied by highway departments individually Library of Congress Control Number 2012934201 or in cooperation with their state universities and others. However, the 2012 National Academy of Sciences. All rights reserved. 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 COPYRIGHT INFORMATION cooperative research. Authors herein are responsible for the authenticity of their materials and for obtaining In recognition of these needs, the highway administrators of the written permissions from publishers or persons who own the copyright to any previously American Association of State Highway and Transportation Officials published or copyrighted material used herein. initiated in 1962 an objective national highway research program Cooperative Research Programs (CRP) grants permission to reproduce material in this employing modern scientific techniques. This program is supported on 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, a continuing basis by funds from participating member states of the FMCSA, FTA, or Transit Development Corporation endorsement of a particular product, Association and it receives the full cooperation and support of the method, or practice. It is expected that those reproducing the material in this document for Federal Highway Administration, United States Department of 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 Transportation. from CRP. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board's recognized objectivity and understanding of NOTICE modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which 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 authorities on any highway transportation subject may be drawn; it the Governing Board of the National Research Council. possesses avenues of communications and cooperation with federal, The members of the technical panel selected to monitor this project and to review this state and local governmental agencies, universities, and industry; its report were chosen for their special competencies and with regard for appropriate balance. relationship to the National Research Council is an insurance of 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 objectivity; it maintains a full-time research correlation staff of specialists by the Governing Board of the National Research Council. in highway transportation matters to bring the findings of research The opinions and conclusions expressed or implied in this report are those of the directly to those who are in a position to use them. researchers who performed the research and are not necessarily those of the Transportation The program is developed on the basis of research needs identified Research Board, the National Research Council, or the program sponsors. by chief administrators of the highway and transportation departments The Transportation Research Board of the National Academies, the National Research and by committees of AASHTO. Each year, specific areas of research Council, and the sponsors of the National Cooperative Highway Research Program do not needs to be included in the program are proposed to the National endorse products or manufacturers. Trade or manufacturers' names appear herein solely because they are considered essential to the object of the report. Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of 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 at: http://www.national-academies.org/trb/bookstore Printed in the United States of America

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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide 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 activities 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 individu- als interested in the development of transportation. www.TRB.org www.national-academies.org

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COOPERATIVE RESEARCH PROGRAMS CRP STAFF FOR NCHRP REPORT 712 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 Andra Briere, Editor NCHRP PROJECT 09-40 PANEL Field of Materials and Construction--Area of Bituminous Materials Gloria Burke, Maryland State Highway Administration, Hancock, MD (Chair) Ronald Collins, Pavement Technology, Inc., Covington, GA Jack E. Cowsert, North Carolina DOT, Raleigh, NC Dale S. Decker, Dale S. Decker, LLC, Eagle, CO Roger C. Olson, Minnesota DOT, Maplewood, MN Murari M. Pradhan, Arizona DOT, Phoenix, AZ Gregory A. Sholar, Florida DOT, Gainesville, FL Matthew Corrigan, FHWA Liaison Frederick Hejl, TRB Liaison AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 9-40. The Louisiana Transpor- tation Research Center (LTRC) of Louisiana State University was the contractor for this study. Texas A&M University and James A. Scherocman were subcontractors. The authors of the report are Louay N. Mohammad (LTRC), Mostafa A. Elseifi (LSU), Abraham Bae (LTRC), Nachiketa Patel (LSU), Joe Button (Texas A&M University), and James A. Scherocman (private consultant). Louay N. Mohammad was the Principal Investigator. The research team gratefully acknowledges the participation and cooperation of state departments of transportation and industry associations who responded to the questionnaire survey on tack coat applica- tion practices.

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FOREWORD By Edward Harrigan Staff Officer Transportation Research Board This report presents proposed test methods for measuring the quality and performance characteristics of tack coat in the laboratory and the field, as well as a training manual present- ing proposed construction and testing procedures for tack coat materials. Thus, the report will be of immediate interest to staff of state highway agencies, materials suppliers, and paving contractors with responsibility for selection, testing, and use of tack coat materials. _________________________________________________________________________ NCHRP Project 9-40, "Optimization of Tack Coat for HMA Placement," was conducted by the Louisiana Transportation Research Center, Baton Rouge, Louisiana, with major par- ticipation by the Texas Transportation Institute, College Station, Texas, and consultant James A. Scherocman, Cincinnati, Ohio. The objectives of this research were to determine optimum application methods, equip- ment type and calibration procedures, application rates, and asphalt binder materials for the various uses of tack coats and to propose new or revised AASHTO methods and prac- tices related to tack coats. In accomplishing these objectives, both present and emerging technology in the United States and worldwide was evaluated. In the research, the contractor developed two new test methods and associated criteria for characterizing the quality and performance of tack coat materials: the Louisiana Tack Coat Quality Tester (LTCQT) and the Louisiana Interlayer Shear Strength Test (LISST). The LTCQT is a small test unit that can measure the bond strength of a tack coat in the field. The LISST is a test fixture fitted into a universal testing machine to measure the interface shear strength (ISS) of a tack coat in a field or laboratory specimen. With the LISST, the effects of pavement surface types and conditions, tack coat material types, and tack coat application rates and methods on tack coat performance can be assessed. The research demonstrated a strong direct relationship between the ISS and the residual application rate of a wide range of tack coat materials, including a PG 64-22 asphalt binder, and trackless, CRS-1, SS-1, and SS-1h emulsions. Similarly, the LISST results show that for a given tack coat material the ISS is directly related to the pavement surface roughness. Finally, the research established a proposed minimum laboratory-measured ISS to provide acceptable tack coat performance in the field as well as optimal tack coat residual applica- tion rates for different pavement surface types. The report fully documents the research leading to the proposed LTCQT and LISST test methods and associated quality and performance criteria, and includes four appendixes: Appendix A: Worldwide Survey Questionnaire Appendix C: Standard Test Method for Assessing Tack Coat Installation Quality using the LTCQT

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Appendix E: Standard Test Procedure for Measuring Interface Bond Strength in the Labora- tory using the LISST Appendix F: Training Manual In addition, two appendixes are available for download from the NCHRP Project 9-40 web page at http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=974: Appendix B: ATackerTM Displacement Rate Verification Experiment Appendix D: Comparison of the LISST Device and the Simple Shear Tester (SST)

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CONTENTS 1 Summary 4 Section 1 Introduction and Research Approach 4 1.1. Problem Statement 4 1.2. Research Objective 4 1.3. Research Scope 5 1.4. Research Approach 7 Section 2 State of Practice 7 2.1. Tack Coat Materials 8 2.2. Tack Coat Application Rate 8 2.3. Tack Coat Breaking and Setting Time 9 2.4. Tack Coat Application Methods 9 2.4.1Equipment 10 2.4.2 Proper Tack Coat Application 11 2.5. Characterization of Tack Coat Application 11 2.5.1 Laboratory Characterization of Tack Coats 14 2.5.2 Interface Bond Strength and Tack Coat Film Test Devices 14 2.6. Worldwide Survey 19 Section 3 Experimental Program 19 3.1.Introduction 19 3.2. Tack Coat and Overlay Construction at the Test Site 19 3.2.1 HMA Pavement Surface Preparation 20 3.2.2 Dusty and Wet Conditions Simulation 20 3.2.3 Tack Coat Application 22 3.2.4 Overlay Construction 24 3.2.5 Quality Testing of Tack Coat Application 24 3.2.6 Specimen Coring and Conditioning 27 3.3. Experiment Plan I: Development of a Test Device to Evaluate the Quality of the Bond Strength of Tack Coat Spray Application in the Field 28 3.4. Experiment Plan II: Rheological Properties and Superpave PG of Tack Coat Materials 28 3.5. Experiment Plan III: Development of a Laboratory Test Procedure to Measure the Interface Bond Strength 28 3.6. Experiment Plan IV: Effects of Test Temperature and Its Relationship with Tack Coat Rheology 30 3.7. Experiment Plan V: Effects of Pavement Surface Type and Sample Preparation Method 30 3.8. Experiment Plan VI: Effects of Surface Texture and Permeability on Interface Shear Strength 32 3.9. Theoretical Investigation

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35 Section 4 Findings 35 4.1. Findings of the Worldwide Survey 35 4.1.1 Types and Grades of Commonly Used Tack Coat Materials 35 4.1.2 Types of Tack Coat Applied to Different Pavement Surfaces 37 4.1.3 Findings Related to Tack Coat Application Methods 44 4.1.4 Findings Related to Tack Coat Application 45 4.2. Experiment I: Development of a Test Device to Evaluate the Quality of the Bond Strength of Tack Coat Spray Application in the Field 46 4.2.1 First Generation of LTCQT 46 4.2.2 Second Generation of LTCQT 48 4.2.3 Development of Tack Coat Test Procedure Using LTCQT 49 4.2.4 LTCQT Test Procedure 49 4.2.5 Effect of Tack Coat Temperature on the Ultimate Tensile Strength 51 4.3. Experiment II: Rheological Properties of Tack Coat Materials and Its Relationship to Bond Strength 52 4.3.1 Superpave Grading of Emulsified Tack Coats 52 4.3.2 Relationship Between LTCQT Test Results and Tack Coat Rheological Properties 53 4.3.3 Measurements of Tack Coat Bond Strength at the Softening Point 53 4.4. Experiment III: Development of a Laboratory Test Procedure to Measure the Interface Bond Strength 55 4.4.1 Effects of Tack Coat Characteristics on Interface Shear Strength 58 4.4.2 Effect of Confining Pressure 60 4.4.3 Effect of Dusty Conditions of HMA Surface 61 4.4.4 Effect of Wet (Rainfall) Conditions of Tacked Surface 61 4.4.5 Effects of Tack Coat Coverage 61 4.5. Experiment IV: Effects of Test Temperature and Its Relationship with Tack Coat Rheology 61 4.5.1 Interface Bond Strength at Various Temperatures 65 4.5.2 Interface Stiffness Characteristics at Various Temperatures 65 4.5.3 Relationship Between Interface Shear Strength and Tack Coat Rheology 66 4.6. Experiment V: Effects of Pavement Surface Type and Sample Preparation Method 66 4.6.1 Effects of Tack Coat Type and Residual Application Rate 68 4.6.2 Effects of Surface Type 68 4.6.3 Effects of Surface Wetness 69 4.6.4 Effects of Preparation Methods 69 4.7. Experimental VI: Effects of Texture and Permeability on Tack Coat Bond Strength 72 4.8. Theoretical Investigation 80 Section 5 Conclusions 82 References A-1 Appendix A Worldwide Survey Questionnaire B-1 Appendix B ATackerTM Displacement Rate Verification Experiment

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C-1 Appendix C Standard Test Method for Assessing Tack Coat Installation Quality Using the LTCQT D-1 Appendix D Comparison of the LISST Device and the Simple Shear Tester E-1 Appendix E Standard Test Procedure for Measuring Interface Bond Strength in the Laboratory Using the LISST F-1 Appendix F Tack Coat Training Manual 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.