Oregon Department of Transportation (ODOT) has specified performance-based asphalts (PBAs) since 1991. Developed by the Pacific Coast Conference on Asphalt Specifications (PCCAS) in 1990, the PBA concept uses conventional test methods for classification and facilitates binder selection based on climatic conditions. The Conference plan was to use the PBA concept and conventional tests as an interim approach which would eventually be replaced with the Strategic Highway Research Program performance grade (SHRP-PG) specification and supporting tests. As a first step in the SHRP implementation/validation effort ODOT has evaluated its commonly used PBA grades in terms of the SHRP (now called Superpave) protocols. The limited binder evaluation to date suggests the following equivalencies:
Using the Superpave weather database, nomographs were developed to illustrate the recommended binder grades. Because of Oregon's climatic diversity, as many as 14 binder grades could be used. Practical constraints and realistic measures such as state-maintained road-miles associated with the various PG binders, however, suggest that 4 PG binders may suffice. Additionally, preliminary economic analysis suggests that implementation of the PG system could provide substantial savings. Because of Oregon's extensive use of open-graded friction courses, additional work must be done to determine what effects, if any, the PG classification might have on this mix type in terms of field performance.