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Dr. Thomas Bennert
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Due to particulates common in crumb rubber-modified asphalt binders, conventional PG grading using the Dynamic Shear Rheometer (DSR) with a gap height of 1.0 mm may not be valid and in accordance with current specifications. Asphalt binder testing and mixture testing was conducted on binders with and without crumb rubber modification to determine an asphalt binder test method which best matches the mixture performance. It was determined that the Multiple Stress Creep Recovery (MSCR) test, conducted with a gap height of 2.0 mm and at in-service temperatures, best correlated with Flow Number testing in the Asphalt Mixture Performance Tester (AMPT). This relationship was found to be better than that of the current DSR test procedure for high temperature PG grading.