Automated procedure for generation of creep compliance master curve for asphalt mixtures

For the design of asphaltic paving mixtures under heavy traffic loading, the Superpave system specifies use of performance-based mixture tests and prediction models to supplement volumetric mix design procedures. Central to the mechanics-based thermal cracking model used in Superpave is the prediction of thermally induced stresses based on a master curve and shift factor concept. The original version of Superpave had procedures for automated construction of the mixture creep compliance master curve from measured mixture properties. However, recent studies have indicated the need for several new modeling techniques, the development of which has resulted in the need for substantially more sophisticated procedures for automated construction of the master curve. This paper details the development of a computer program called MASTER, which automates master curve construction using built-in logic capabilities designed to handle the wide variety of measured responses encountered in practice. MASTER was found to agree closely with manually determined shift factors for 36 field mixtures investigated. The program was also found to be extremely robust, producing rational shift factors even when used to analyze complicated, thermally damaged materials. On the basis of these findings, the procedures developed here are recommended for inclusion in future revisions of the Superpave performance modeling software.