High-Temperature Properties of Asphalt Binders: Comparison of Multiple Stress Creep Recovery and Performance Grading Systems

Abstract

The Superpave® high-temperature test protocol has been shown to be inadequate for characterizing the high-temperature behavior of asphalt binders, particularly those that are polymer modified. Recently, a specification based on the multiple stress creep recovery (MSCR) test was proposed to address the shortcomings of the Superpave high-temperature binder specifications. This study aimed to investigate the merits of implementing the current MSCR test protocol as a replacement for the performance-graded high-temperature test. A statistical analysis was conducted on a data set from the Indiana Department of Transportation to see how MSCR and performance grading procedures differ in grading various binders. In addition, an experimental study was conducted with 16 modified and unmodified binders. The results indicated that the MSCR test was a suitable replacement for the performance grade test because it provided a better tool to rank modified asphalt binders as well as unmodified ones. That is, creep compliance from the MSCR test more fundamentally represented binder behavior at high temperatures compared with the performance grade rutting parameter. In addition, the simplified approach—known as grade-bumping—used in the current Superpave mix design system to account for high traffic levels and low speed limits can be eliminated when the MSCR test is used.