The Superpave Mix Design System: Anatomy of a Research Program (2012)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

ACKNOWLEDGMENT This work was sponsored by the American Association of State Highway and Transportation Officials (AASHTO), in cooperation with the Federal Highway Administration, and was conducted in the National Cooperative Highway Research Program (NCHRP), which is administered by the Transportation Research Board (TRB) of the National Academies. 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, Transit Development Corporation, or AOC 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. DISCLAIMER The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research. They are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The information contained in this document was taken directly from the submission of the author(s). This material has not been edited by TRB.

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

i CONTENTS List of Tables .............................................................................................................................. v Author Acknowledgments ......................................................................................................... vi Abstract ..................................................................................................................................... vii Executive Summary ................................................................................................................. viii Research Approach .................................................................................................................... ix Research Findings ...................................................................................................................... ix CHAPTER 1. BACKGROUND ..................................................................................................... 1 1.1 Purpose of this History......................................................................................................... 1 1.2 APPROACH ......................................................................................................................... 2 1.2.1 Technical Issues in this Report ...................................................................................... 3 1.3 Applicability of Results to Practice ..................................................................................... 3 CHAPTER 2. TIMELINE OF THE SUPERPAVE PROGRAM ................................................... 4 2.1 Major Players and Roles ...................................................................................................... 4 CHAPTER 3. PRE-RESEARCH PHASE (1980-1987) ................................................................. 6 3.1 Seeds of the Research Program ............................................................................................. 6 3.1.1 Structuring the Research Program ................................................................................ 7 3.1.2 Funding and Organization............................................................................................. 7 3.2 SHRP’s Colorful Precursors – The “Blue” and “Brown” Books ........................................ 8 3.2.1 The “Blue Book”....................................................................................................... 8 3.2.2 The “Brown Book” ................................................................................................. 12 Chapter 4. RESEARCH PHASE................................................................................................... 20 4.1 Asphalt Program Structure and Staffing ........................................................................ 20 4.2 Evolution and Organization of the Research Program ................................................... 20 4.2.1 Contracting Plan...................................................................................................... 21 4.2.2 Materials Reference Library ................................................................................... 28 4.2.3 Validation and Analysis of Research Data ............................................................. 31 4.2.4 Midcourse Assessment............................................................................................ 35 4.3 Binder-Related Research ................................................................................................ 37 4.3.1 Guiding Philosophy ................................................................................................ 37 4.3.2 Hypotheses and Models Employed in the Binder Research ................................... 37 4.3.3 Evolution of Binder Specification .......................................................................... 41

4.4 Asphalt-Aggregate Mix Related Research ..................................................................... 44 4.4.1 Guiding Philosophy ................................................................................................ 44 4.4.2 Hypotheses and Models Employed in the Mix Research ....................................... 48 4.5 Products .......................................................................................................................... 50 What’s In a Name?................................................................................................................ 51 4.5.1 Binder Specification and Supporting Tests............................................................. 52 4.5.2 Other Binder-Related Products ............................................................................... 55 4.5.3 Mix Design System and Software........................................................................... 55 4.5.4 Modifier Evaluation Protocol ................................................................................. 58 4.5.5 The Gyratory Story ................................................................................................. 59 4.5.6 The Delphi Story ..................................................................................................... 77 4.5.6.1 The Delphi Method ................................................................................................. 79 4.5.7 Products from Studies of Moisture Damage: NAT and AASHTO T 283 ............. 82 4.6 People and Organizations ........................................................................................... 89 4.6.1 Canadian Strategic Highway Research Program .................................................... 89 4.6.2 Graduate Students ................................................................................................... 91 4.6.3 Loaned Staff ............................................................................................................ 91 4.7 Reflections on the Research Process – Hindsight is 20-20 ............................................ 92 CHAPTER 5. IMPLEMENTATION PHASE .............................................................................. 95 5.1 Seeds of Implementation during the Research Phase..................................................... 95 5.2 Transition to Implementation ..................................................................................... 97 5.2.1 Transition to Implementation at SHRP Program Office ......................................... 97 5.2.2 Transition to Implementation at FHWA ............................................................... 100 5.3 Focused Implementation Begins: The ISTEA Years................... ............................. 105 5.3.1 Funding and Managing the Implementation Phase ............................................... 105 5.3.2 Implementation in Full Swing ............................................................................. 109 5.4 Key Groups and Activities for Implementation ....................................................... 110 5.4.1 AASHTO .............................................................................................................. 110 5.4.2 Lead States Team (1996-2000) ............................................................................. 113 5.4.3 Superpave Centers ................................................................................................ 122 5.4.4 TRB/NCHRP ........................................................................................................ 126 5.4.5 User-Producer Groups .......................................................................................... 127 5.4.6 Technical Working Group and Expert Task Groups ............................................ 130 5.4.7 Asphalt Institute .................................................................................................... 133

5.4.8 NAPA and the Construction Industry ................................................................... 134 5.4.9 SPS-9 Projects ....................................................................................................... 136 5.4.10 Universities ............................................................................................................. 137 5.4.11 Conferences and Workshops................................................................................... 138 5.5 Implementation at Risk – the TEA-21 Years ........................................................... 141 5.5.1 Background ........................................................................................................... 141 5.5.2 TRB Superpave Committee .................................................................................. 142 5.5.3 The ETGs under TEA-21 ...................................................................................... 144 5.5.4 Survival ................................................................................................................. 144 5.5.5 Superpave 2005 ..................................................................................................... 145 5.6 Technology Advancements and Challenges during Implementation ....................... 147 5.6.1 Binder Testing and Specifications ........................................................................ 148 5.6.2 Mixture Testing and Specifications .................................................................. 149 5.6.3 Performance Testing ............................................................................................. 150 5.6.4 Construction .......................................................................................................... 151 5.7 Where are We Today? .............................................................................................. 155 5.7.1 Binders .................................................................................................................. 155 5.7.2 Mixtures and Construction .................................................................................... 155 5.7.3 Models................................................................................................................... 156 5.7.4 Construction .......................................................................................................... 156 Chapter 6. LESSONS LEARNED.............................................................................................. 157 6.4 Clearly Appreciate Problem Scope, Size and Complexity ....................................... 159 6.5 Base Decisions on Objective Data ............................................................................ 161 6.6 Provide Strong Technical Leadership ....................................................................... 162 6.7 Anticipate the Politics of Ideas........ ......................................................................... 162 6.8 Develop a Team Philosophy ..................................................................................... 164 6.9 Expect Researchers to be Solely Dedicated to the Research Effort... ....................... 166 6.10 Build a Cooperative Community .............................................................................. 166 6.11 Find a Champion for the Research Results.......................... ..................................... 167 6.12 Recognize Size of the Implementation Effort .......................................................... 168 6.13 Cultivate Continued Support for Programs (Both Financial and Intellectual) ......... 169 6.14 Involve Researchers in Implementation Effort ......................................................... 170 6.15 Communicate with the Intended Audience .............................................................. 170 6.16 Get the Technology Out to the Audience ................................................................. 170

6.17 Benchmark ................................................................................................................ 171 6.18 Concluding Observations ......................................................................................... 171 Appendixes A-E Please note: The appendixes will be available on the TRB web site (www.trb.org) on the project page for NCHRP Project 9-42. Appendix A List of Interviewees Appendix B Committee and ETG Rosters Appendix C Photographs of Superpave Research Appendix D History of Mix Design Appendix E Transcript of the Reno Conference

LIST OF TABLES Table 1 Proposed Asphalt Projects, Tasks and Budgets (after SHRP Research Plans (1)) 17 Table 2 Major Asphalt Research Contracts: Proposed vs Actual (based on 1 and 4) 23 Table 3 Major Asphalt Contracts (4) 24 Table 4 AIIR (Asphalt, Independent, Innovative Research) Supporting Asphalt Contracts (4) 25 Table 5 Performance Graded Asphalt Binder specification (AASHTO MP 1) 53 Table 6 Comparison of Level 2 and Level 3 Mix Design Methods 58 Table 7 NCHRP 9-6(1) AAMAS Comparison of Air Void Gradient (Difference between Middle of Specimen and Lowest Third) (11) 70 Table 8 Density Gradient in Specimen Compacted on Prototype Gyratory Compactor (14) 71 Table 9 Recommended NAT Criteria 83 Table 10 Canadian Participants in SHRP Pre-Implementation Studies 90 Table 11 Detailed Steps in the SHRP Program Office Implementation Plan (After Kulash, 1992) 98 Table 12 Members of AASHTO Task Force on SHRP Implementation 112 Table 13 Members of the Lead State Team for Superpave (24) 114 Table 14 Superpave Lead State Team Goals and Strategies 116 Table 15 Lead State Team Workshops 117 Table 16 Asphalt Mixture Expert Task Group Meetings 131 Table 17 Members of the TRB Superpave Committee 143 Table 18 WesTrack Forensic Team Members 153

Author Acknowledgments The research reported herein was performed under NCHRP Project 9-42 by the North Central Superpave Center (NCSC) at Purdue University as the prime contractor. TDC Partners of Alexandria, Virginia, was the subcontractor on the project and, in turn, had subcontracts with Nichols Consulting Engineers, Fugro Consultants, Inc., and the Heritage Research Group. Dr. Rebecca S. McDaniel, Technical Director of the NCSC, was the principal investigator. The other authors are Dr. Rita B. Leahy, formerly with Nichols Consulting Engineers and now with the California Asphalt Pavement Association; Mr. Gerald A. Huber, of the Heritage Research Group; Mr. James S. Moulthrop of Fugro Consultants, Inc.; and Mr. Ted Ferragut, principal of TDC Partners, Inc., now retired. Numerous people – too numerous to mention individually – participated in interviews and shared their records, logs and files. Their support is greatly appreciated. Ron Cominsky deserves special mention for opening his extensive files to our review. A few individuals, including Bob McGennis, also reviewed sections of the report to verify its accuracy. Their input is also greatly appreciated.

ABSTRACT The asphalt research program conducted as part of the Strategic Highway Research Program was the most focused asphalt research program ever. Intense research activity over a nominal five-year period at a cost of $50 million dollars led to sweeping changes in how asphalt materials are specified, tested and designed. The products of this research, known collectively as the Superpave mix design system or simply Superpave, are used across the US and internationally. This report describes how such a large-scale research effort was conceived, funded, and managed. It outlines the research and implementation efforts that brought the products into routine use. Lastly, it summarizes some of the key lessons learned in the process of conducting such a large-scale program. The findings outlined in this report were garnered through interviews with over 70 people who were involved in the research and implementation efforts as well as reviewing reports, letters, diaries, meeting minutes and other documents.

EXECUTIVE SUMMARY The Strategic Highway Research Program (SHRP, pronounced “Sharp”) was an unprecedented research effort. It was the largest, most highly focused research effort in the United States since the AASHO Road Test of the late 1950s and went far beyond the Road Test in its breadth and scope. While SHRP was aimed at developing high-payoff products in six focused areas of national need, the Asphalt Research Program was the largest effort in terms of funding and was arguably the most successful. This program eventually led to the development of the Superpave system for the design of asphalt mixtures, which has changed asphalt technology in the U.S. and has had an impact around the world. Superpave has created change in the entire asphalt industry, including asphalt binder suppliers, aggregate suppliers, hot-mix producers, contractors, and specifying agencies at all levels. Superpave introduced new concepts for material testing and selection, new test protocols, new equipment, a new mix design method and new performance testing tools. Implementation has required substantial investments in equipment and training far exceeding the initial research investment. In fact, the implementation process is still ongoing today (2011), over 18 years since the conclusion of the research. The SHRP Asphalt Research Program was a success not only because of its technical developments but also as a result of its organization. The methods of funding, administration, organization, and decision-making all contributed to its success, though some elements of the program were certainly less successful than others. Perhaps SHRP’s greatest achievement is the implementation of its research results. From the outset, SHRP’s objective was to implement the technology that was developed. The focus of the entire research effort was on high-payoff, implementable research results. As a result, some efforts to initiate implementation began before the research was completed, at times to the consternation of the asphalt community. This report summarizes the findings of a study to document the history of the SHRP Asphalt Research Program from the initiation of the research through the eventual implementation and refinements of its products. The report also addresses the organizational structure of this large-scale program. This report is not a critique of the research results. Instead, it is intended to document the processes used to develop the research products and the methods used to resolve the technical and organizational barriers encountered. It is hoped that this accounting of the technical decisions made during SHRP will provide an understanding of how the Superpave mix design system came together and will identify where refinements may be possible in the future. In some instances, decisions had to be made to pursue one path over another due to budgetary, time, or technological constraints. As technological advances occur in the future, or as time and funding become available, these alternate paths may be fruitful areas of inquiry. Second, understanding the successes and disappointments of SHRP can help with the design of future focused research programs and implementation efforts.