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NAT IONAL COOPERAT IVE H IGHWAY RESEARCH PROGRAM NCHRP SYNTHESIS 445 Practices for Unbound Aggregate Pavement Layers A Synthesis of Highway Practice Consultant Erol Tutumluer University of IllinoisâUrbana-Champaign Urbana, Illinois TRANSPORTATION RESEARCH BOARD WASHINGTON, D.C. 2013 www.TRB.org Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration subsCriber Categories Geotechnology â¢ Highways â¢ Materials
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. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Boardâs recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state, and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National 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 NCHRP SYNTHESIS 445 Project 20-05, Topic 43-03 ISSN 0547-5570 ISBN 978-0-309-27085-4 Library of Congress Control Number 2013936323 Â© 2013 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, FTA, or Transit Development Corporation 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 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 the Governing Board of the National Research Council. The members of the technical panel selected to monitor this project and to review this report were chosen for their special competencies and with regard for appropriate balance. 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 Governing Board of the National Research Council. 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 Research Council, or the program sponsors. The Transportation Research Board of the National Academies, the National Research Council, and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of the report. NOTE: The Transportation Research Board of the National Academies, the National Research Council, the Federal Highway Administration, the American Association of State Highway and Transportation Officials, and the individual states participating in the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of this report.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished schol- ars 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 techni- cal 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 Acad- emy 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 achieve- ments of engineers. Dr. C. D. Mote, Jr., 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 Academyâs purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Acad- emy, 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. C. D. Mote, Jr., 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 Transportation Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisci- plinary, and multimodal. The Boardâs 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 Transporta- tion, and other organizations and individuals interested in the development of transportation. www.TRB.org www.national-academies.org
TOPIC PANEL 43-03 JUDITH B. CORLEY-LAY, North Carolina Department of Transportation, Raleigh ERVIN L. DUKATZ, JR., Mathy Construction, Onalaska, WI GEORGENE M. GEARY, Georgia Department of Transportation, Forest Park AMIR N. HANNA, Transportation Research Board G.P. JAYAPRAKASH, Transportation Research Board MIKE POLODNA, Washington State Department of Transportation, Tumwater DANESH SAJEDI, Maryland State Highway Administration, Hanover NANCY M. WHITING, Purdue University, West Lafayette, IN RICHARD C. MEININGER, Federal Highway Administration (Liaison) FRANK M. RICH, Federal Highway Administration (Liaison) SYNTHESIS STUDIES STAFF STEPHEN R. GODWIN, Director for Studies and Special Programs JON M. WILLIAMS, Program Director, IDEA and Synthesis Studies JO ALLEN GAUSE, Senior Program Officer GAIL R. STABA, Senior Program Officer DONNA L. VLASAK, Senior Program Officer TANYA M. ZWAHLEN, Consultant DON TIPPMAN, Senior Editor CHERYL KEITH, Senior Program Assistant DEMISHA WILLIAMS, Senior Program Assistant DEBBIE IRVIN, Program Associate COOPERATIVE RESEARCH PROGRAMS STAFF CHRISTOPHER W. JENKS, Director, Cooperative Research Programs CRAWFORD F. JENCKS, Deputy Director, Cooperative Research Programs NANDA SRINIVASAN, Senior Program Officer EILEEN P. DELANEY, Director of Publications NCHRP COMMITTEE FOR PROJECT 20-05 CHAIR CATHERINE NELSON, Oregon DOT MEMBERS KATHLEEN S. AMES, Michael Baker, Jr., Inc. STUART D. ANDERSON, Texas A&M University BRIAN A. BLANCHARD, Florida DOT CYNTHIA J. BURBANK, PB Americas LISA FREESE, Scott County (MN) Community Services Division MALCOLM T. KERLEY, Virginia DOT RICHARD D. LAND, California DOT JOHN M. MASON, JR., Auburn University ROGER C. OLSON, Minnesota DOT ROBERT L. SACK, New York State DOT FRANCINE SHAW-WHITSON, Federal Highway Administration LARRY VELASQUEZ, JAVEL Engineering, Inc. FAA LIAISONS JACK JERNIGAN MARY LYNN TISCHER TRB LIAISON STEPHEN F. MAHER Cover figure: Work is conducted on a pavement test study at the Advanced Transportation Research and Engineering Laboratory of the University of Illinois at UrbanaâChampaign. Photo by the Illinois Center for Transportation, Advanced Transportation Research and Engineering Laboratory, University of Illinois at UrbanaâChampaign.
FOREWORD PREFACE By Jon M. Williams Program Director Transportation Research Board Properly designed and constructed unbound aggregate layers have the potential to improve pavement performance and longevity. This study gathers information on the current state of practice and research on unbound aggregate. The study finds that no common prac- tice exists among state transportation agencies. Accordingly, the report summarizes important aspects and effective practices related to material selection, design, and construction of unbound aggregate layers. Prevalent agency practices are summarized and key lessons learned from research studies are highlighted. Information for this study was acquired through a literature review and surveys of state and Canadian transportation agencies. Erol Tutumluer, University of Illinois at UrbanaâChampaign, collected and synthesized the information and wrote the report. The members of the topic panel are acknowledged on the preceding page. This synthesis is an immediately useful document that records the practices that were acceptable within the limitations of the knowledge available at the time of its preparation. As progress in research and practice continues, new knowledge will be added to that now at hand. Highway administrators, engineers, and researchers often face problems for which infor- mation already exists, either in documented form or as undocumented experience and prac- tice. This information may be fragmented, scattered, and unevaluated. As a consequence, full knowledge of what has been learned about a problem may not be brought to bear on its solution. Costly research findings may go unused, valuable experience may be overlooked, and due consideration may not be given to recommended practices for solving or alleviating the problem. There is information on nearly every subject of concern to highway administrators and engineers. Much of it derives from research or from the work of practitioners faced with problems in their day-to-day work. To provide a systematic means for assembling and evaluating such useful information and to make it available to the entire highway commu- nity, the American Association of State Highway and Transportation Officialsâthrough the mechanism of the National Cooperative Highway Research Programâauthorized the Transportation Research Board to undertake a continuing study. This study, NCHRP Project 20-5, âSynthesis of Information Related to Highway Problems,â searches out and synthesizes useful knowledge from all available sources and prepares concise, documented reports on specific topics. Reports from this endeavor constitute an NCHRP report series, Synthesis of Highway Practice. This synthesis series reports on current knowledge and practice, in a compact format, without the detailed directions usually found in handbooks or design manuals. Each report in the series provides a compendium of the best knowledge available on those measures found to be the most successful in resolving specific problems.
CONTENTS 1 SUMMARY 3 CHAPTER ONE INTRODUCTION Introduction and Background, 3 Synthesis Objectives and Study Approach, 4 Transportation Agency Use of Unbound Aggregate Base and Subbase Layers, 5 Outline of Chapters, 7 References, 8 9 CHAPTER TWO AGGREGATE TYPES AND MATERIAL SELECTION Introduction, 9 Aggregate Types and Sources, 9 Stone Deposits, 9 Sand and Gravel Deposits, 10 Supply and Demand for Aggregates in the United States, 10 Aggregate Properties Affecting Unbound Aggregate Layer Behavior, 11 Mineralogy, 11 Particle Size Distribution and Fines Content, 12 Particle Shape, Surface Texture, and Angularity, 12 Degree of Compaction, 14 Moisture Content, 14 Tests to Check Aggregate Quality for Pavement Applications, 16 Background, 16 Current Practices on Tests to Check the Quality of Aggregate Sources, 17 Sustainable Production and Utilization of Aggregates, 23 Unbound Pavement Applications, 24 Best Value Granular Material Concept, 28 Recycling Aggregates and Recycled Granular Materials, 29 Reclaimed Asphalt Pavement, 30 Recycled Concrete Aggregate, 30 Potential Environmental Impacts from Using Recycled Materials, 32 Recycling of Unbound Aggregate Material from Existing Pavements, 33 Commonly Used Recycled Materials in Unbound Aggregate Base and Subbase Layers, 33 Current State of the Practice Regarding Testing of Recycled Materials, 33 Summary, 35 References, 35 40 CHAPTER THREE GRANULAR BASE AND SUBBASE CONSTRUCTION PRACTICES Introduction, 40 Importance of Standardized Construction Specifications, 40 Aggregate Storage and Construction Practices Affecting Constructed Layer Performance, 40 Aggregate Stockpiling as a Source of Segregation, 40 Construction Practices as a Source of Segregation, 41
Aggregate Degradation and Possible Sources, 43 Construction Lift Thickness and Its Effect on Compactability, 43 Background, 43 Optimum Construction Lift Thickness, 44 Documented Aggregate Base and Subbase Layer Construction Practices, 45 Inverted Pavements, 45 Conceptual Background, 45 Response Mechanism, 46 Material Specifications and Construction Procedure, 47 Previous Findings on the Benefits of Inverted Pavements, 48 Current State of Practice on Alternative Base Course Construction, 52 Summary, 52 References, 53 55 CHAPTER FOUR UNBOUND AGGREGATE BASE CHARACTERIZATION FOR DESIGN Introduction, 55 Load Transfer in Granular Materials, 55 Unbound Granular Material Behavior Under Repeated Loading, 55 Resilient Response of Unbound Aggregate Layers, 56 Stress States in Unbound Aggregate Layers Under Loading, 56 Compaction-Induced Residual Stresses, 58 Concept of Cross-Anisotropy, 58 Methods to Characterize Unbound Aggregate Layer Behavior, 59 California Bearing Ratio, 59 Static Triaxial Testing, 60 Repeated Load Triaxial Testing, 61 Innovative Devices for Advanced Triaxial Characterization of Unbound Aggregates, 64 Interpretation of Repeated Load Triaxial Test Data, 68 Current Resilient Modulus Models, 68 Current Permanent Deformation Models, 69 Historical Development in Unbound Aggregate Characterization for Pavement Design, 69 1961 Interim Pavement Design Guide, 69 1972 Interim Pavement Design Guide, 69 1986 Pavement Design Guide, 69 1993 Pavement Design Guide, 69 NCHRP 1-37A Pavement Design Guide, 69 DARWin-ME, 70 State of the Practice in Unbound Aggregate Characterization and Design, 70 Background, 70 Conclusions from Survey of Transportation Agencies, 73 State-of-the-Art Methods for Unbound Aggregate Layer Characterization and Design, 74 Stress Path Testing, 74 Directional (Anisotropic) Modulus Testing, 75 Field Validations, 79 Anisotropy as Aggregate Quality Indicator, 81 Consideration of Drainage in Unbound Aggregate Layer Design, 82 Moisture-Related Deterioration, 83 State of the Practice Regarding the Consideration of Drainage and Climatic Effects on Unbound Aggregate Base/Subbase Layers, 86 Effects of Aggregate Material Properties on Layer Permeability, 89 Permeable Base Designs, 89 Consideration of Climatic Conditions in Unbound Aggregate Base Design, 91 Freeze-Thaw and Frost Penetration, 95 References, 95
101 CHAPTER FIVE COMPACTION, QUALITY CONTROL, AND FIELD PERFORMANCE Introduction, 101 Compaction and Quality Control, 101 Theory and Objectives of Compaction, 101 Establishing the Target Density for Field Compaction Control, 101 Compaction Variables and Equipment Types, 103 Measuring In-Place Density of Constructed Unbound Aggregate Layers, 105 Current State of the Practice, 106 In-Place Modulus Measurement of Constructed Aggregate Layers, 108 Modulus-Based Compaction Control, 110 Need for Modulus-Based Compaction Control, 110 Desired Characteristics of a Modulus-Based Compaction Control System, 110 Continuous Compaction Control and Intelligent Compaction, 110 Need for Intelligent Compaction, 111 Synthesis of Past Research and Agency Experience with IC Systems, 112 Quality Assurance Specifications Based on Continuous Compaction Control, 114 Consideration of Suction Effects in Layer Modulus Estimation, 116 Background, 116 Methods for Measuring Soil Suction, 116 References, 117 119 CHAPTER SIX SUMMARY OF CURRENT PRACTICE AND EFFECTIVE PRACTICES Objectives of Synthesis Study, 119 Research Framework, 119 Aggregate Types and Material Selection, 119 Granular Base/Subbase Construction Practices, 119 Unbound Aggregate Base Characterization for Design, 120 Compaction, Quality Control, and Field Performance, 120 Summary of State Practices, 120 Use of Unbound Aggregate Base and Subbase Layers, 120 Material Selection and Construction Practices, 120 Unbound Aggregate Base Characterization for Design, 121 Compaction, Quality Control, and Field Performance, 121 Recycling Aggregates and Recycled Granular Materials, 121 Climatic Effects and Drainage, 122 Future Research and Implementation, 122 Use of Locally Available Marginal and Out-of-Specification Materials, 122 Use of Modulus-Based Construction Quality Control, 122 Use of Intelligent Compaction Techniques, 122 Alternative Base Course Applications Such as Inverted Pavements, 123 Key Lessons and Effective Practices, 123 Material Selection and Quality Testing, 123 Granular Base and Subbase Construction Practices, 123 Unbound Aggregate Base Characterization for Design, 123 Compaction, Quality Control, and Field Performance, 124 125 ACRONYMS 127 APPENDIX A QUESTIONNAIRE 142 APPENDIX B RESPONDENT INFORMATION
144 APPENDIX C SURVEY RESPONSES 172 APPENDIX D REVIEW OF CURRENT RESILIENT MODULUS MODELS 176 APPENDIX E REVIEW OF CURRENT PERMANENT DEFORMATION MODELS 179 APPENDIX F FOLLOW-UP SURVEY ON RESILIENT MODULUS TESTING 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.