“Superpave” is an overarching term for the results of the asphalt research portion of the 1987 – 1993 Strategic Highway Research Program (SHRP). Superpave consists of (1) an asphalt binder specification, (2) an HMA mix design method and (3) HMA tests and performance prediction models. Each one of these components is referred to by the term “Superpave”. This section provides a brief overview and background of Superpave.
Strategic Highway Research Program (SHRP)
In 1987 the U.S. Congress established a 5-year, $150 million applied research program aimed at improving the performance, durability, safety, and efficiency of the Nation’s highway system. Called the Strategic Highway Research Program (SHRP), this program was officially authorized by the Surface Transportation and Uniform Relocation Act of 1987 and consisted of research concentrated in four key areas (FHWA 1998):
- Asphalt. This area consists of research to develop a completely new approach to HMA mix design.
- Concrete and structures. This area consists of research in the areas of mix design and assessing, protecting and rehabilitating concrete pavements and structures.
- Highway operations. This area consists of pavement preservation, work zone safety and snow and ice control research.
- Pavement performance. This area consists of the Long Term Pavement Performance Program (LTPP), a 20-year study of over 2,000 test sections of in-service U.S. and Canadian pavements to improve guidelines for building and maintaining pavements.
SHRP research activities were completed in 1992 and SHRP was closed down in 1993. To date, SHRP has produced more than 100 new devices, tests and specifications and, perhaps more importantly, has spawned a full-scale on-going implementation drive by such organizations as the FHWA, AASHTO and TRB.
The SHRP asphalt research program, the largest SHRP program at $53 million (FHWA 1998), had three primary objectives (NECEPT 2004):
- Investigate why some pavements perform well, while others do not.
- Develop tests and specifications for materials that will out-perform and outlast the pavements being constructed today.
- Work with highway agencies and industry to have the new specifications put to use.
The final product of this research program is a new system referred to as “Superpave”, which stands for SUperior PERforming Asphalt PAVEments. Superpave, in its final form consists of three basic components:
- An asphalt binder specification. This is the PG asphalt binder specification.
- A design and analysis system based on the volumetric properties of the asphalt mix. This is the Superpave mix design method.
- Mix analysis tests and performance prediction models. This area took much longer to complete and some may argue that it was never fully complete.
Each one of these components required new specifications and performance standards as well as new testing methods and devices.
In 2006, congress established the second strategic highway research program (SHRP 2) to investigate the underlying causes of highway crashes and congestion in a short-term program of focused research. SHRP 2 focus areas are: safety, renewal, reliability and capacity. More on SHRP 2.