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.

RESEARCH APPROACH The SHRP Asphalt Research program generated thousands of pages of reports, meeting minutes, papers, articles, and more. In documenting the history of this program, the research team reviewed written documents from published sources. In addition, the team reviewed the personal files, notes, and diaries of many of the key personnel involved in the program. The team also searched through archives of slides, notes from presentations, and other documents held at TRB, FHWA, and elsewhere. Much of the story behind such a large-scale research program as the SHRP Asphalt Research program, however, is never written down. To gather this unwritten information, the research team conducted over 70 interviews with key personnel from all aspects of the program. Subjects of these interviews included key researchers and graduate students involved in the research, the management staff of the SHRP office, FHWA staff, hot-mix producers, binder and aggregate suppliers, state Department of Transportation personnel, equipment manufacturers, industry association representatives and others. Most interviews were conducted in person, but some were done by telephone between April 2006 and September 2010. Notes from most interviews were reviewed by the subjects to ensure accuracy. Each interview provided an insight into the program from a different perspective, yet common themes emerged from the disparate quarters. These insights and themes are reflected in this report. Three major phases of work are described here to provide a complete picture of the program. The pre-research phase, prior to 1987, was when the seeds of the program were sown. The research phase began in 1987 and lasted into 1993. Implementation was considered during the final years of the research phase, but the main implementation phase began in 1993. (These phases are more fully defined in Chapter 2 and described individually in some detail in Chapters 3, 4 and 5.) RESEARCH FINDINGS This report summarizes how the SHRP Asphalt Research Program products – the Performance-Graded binder specification, the Superpave mix design system, and supporting test protocols and equipment – were developed and evolved. The implementation of the products of this research program stimulated change in every facet of the asphalt industry. Superpave pavements have been shown to perform better, in general, than previous mixes. Overall, Superpave is recognized as one of the major success stories of SHRP. Not all of the technical efforts under the Asphalt Research Program were entirely successful, however. The planned performance prediction models are still being sought through other research efforts. Moisture damage still occurs in pavements, and there is no widely accepted test method to prevent its occurrence. From a non-technical viewpoint, there were ancillary benefits of the SHRP Program. Many young engineers and researchers were brought into the research and/or implementation efforts at an early stage and have gone on to have illustrious careers. More established researchers were able to make a mark and solidify their reputations. And, as might be expected in such a large-scale, cutting-edge effort, egos clashed and disputes arose from time to time. In addition, the review revealed a number of lessons learned. In fact, the main findings of this project may best be expressed as lessons learned through the entire research and

implementation effort stretching over a period of more than 20 years. The following lessons may benefit future large-scale research programs. • Make decisions transparent and firm. • Document the decisions made. • Ensure strong technical leadership with management skills • Have a clear vision of the scope, size and complexity of the problem. • Recognize the “politics of ideas” and that researchers will defend their positions. • Develop an atmosphere fostering teamwork and cooperation rather than competition. • Try to ensure researchers have the time and resources to be dedicated to the effort. • For major issues, consider forming research hubs to help develop a sense of partnership or explore technological options to do the same. • Buffer the competing interests of various stakeholders – balance risk and reward. • Build a cooperative community to help others adopt the new technology. • Recognize the size of the implementation effort – it may be even greater than the size of the research endeavor. • Ensure continued support for the implementation process. • Involve researchers in the implementation effort and users in the research effort. • Communicate clearly with the eventual users of the research results– give them an idea of what is coming but make it clear what is preliminary and what is ready to implement. • Get the technology out to the users – strawman specifications, first article procurements and pooled-fund equipment buys are very effective strategies to get people to try new technologies and get feedback to refine the products. • Benchmark the status before, during and after implementation to document the success – or lack thereof – of the research and implementation effort.

1 CHAPTER 1. BACKGROUND 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 the 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. 1.1 PURPOSE OF THIS HISTORY This project was initiated to document the asphalt technology developed and implemented through the SHRP Asphalt Program and the processes used throughout the research and implementation efforts. The focus is on the Asphalt Research Program in particular. In discussing some organizational and administrative issues, however, some comments may apply to the SHRP Program in general. This report is not a technical 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 system came together and will identify where refinements may still 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

2 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. 1.2 APPROACH The SHRP Asphalt Research program generated thousands of pages of reports, meeting minutes, papers, articles and more. In documenting the history of this program, the research team reviewed written documents from published sources. In addition, the team reviewed the personal files, notes and diaries of many of the key personnel involved in the program who were kind enough to grant access to their files. The team also searched through archives of slides, notes from presentations and other documents held at TRB, FHWA and elsewhere. Much of the story behind such a large-scale research program as the SHRP Asphalt Research program, however, is never written down. To gather this unwritten information, the research team conducted over 70 interviews with key personnel from all aspects of the program. (A listing of the people interviewed is included in Appendix A.) Subjects of these interviews included key researchers and graduate students involved in the research, the management staff of the SHRP office, FHWA staff, hot-mix producers, binder and aggregate suppliers, state Department of Transportation personnel, equipment manufacturers, industry association representatives and others. (Many of those interviewed are pictured in the photographs in Appendix C.) Most interviews were conducted in person, but some were done by telephone between April 2006 and September 2010. Notes from most interviews were reviewed by the subjects to ensure accuracy. Each interview provided an insight into the program from a different perspective, yet common themes emerged from the disparate quarters. These insights and themes are reflected in this report. Three major phases of work are described here to provide a complete picture of the program. The pre-research phase, prior to 1987, was when the seeds of the program were sown. The research phase began in 1987 and lasted into 1993. Implementation was considered during the final years of the research phase, but the main implementation phase began in 1993. These phases will be more fully defined in Chapter 2. Each of these phases is investigated and documented in this report in Chapters 3, 4 and 5. The report is generally structured by topic areas within a chronological framework. In other words, within the three phases, topics including binders, mixtures (including aggregates, performance testing and modeling) and construction (in the implementation phase) are addressed. The history will also examine linkages and interrelationships between the different phases and topics. Finally, the report will conclude with a discussion of the lessons learned in both technical and programmatic terms. The benefits and pitfalls of a large-scale research program will be explored, and recommendations for the conduct of future research and implementation projects will be offered.

3 1.2.1 Technical Issues in this Report This report is not intended as a technical critique of the research results; hence it does not focus on deep discussion of the research findings. Some level of detail, however, is necessary to tell the story of how the Superpave system was developed and implemented. Those who want detailed technical information on how the research was conducted and the significance of the findings should refer to the project reports that are listed in the references. Readers who are not familiar with asphalt materials and mixtures may want to review Appendix D, which describes how asphalt mix design works. In some cases, anecdotes or “stories” have been included to illustrate some of the behind- the-scenes discussions and issues. These are presented in a less formal style than typically used in a technical report because they are not necessarily technical issues and, frankly, to make them more entertaining for the reader. These anecdotes have been set off in boxes to emphasize that they are somewhat peripheral to the main story. 1.3 APPLICABILITY OF RESULTS TO PRACTICE There are two key benefits or ways the results of this project can be used:  The SHRP Asphalt Research Program was one of the most successful research and implementation projects in the history of the US highway program. As such, this history will document how the Superpave system came to be and how its implementation was promoted. It will summarize the decisions made, as well as how and why they were made. This may identify promising lines of research that were not or could not be pursued due to various constraints (technical and non-technical, such as time, funding, technology, “politics,” etc.)  This history will also describe the processes and organizational features that worked or did not work in both the research and implementation phases. This assessment of the administration of the program can serve as a guide for future research and implementation efforts.