Performance of Modified Asphalt Binders with Identical High-Temperature Performance Grades but Varied Polymer Chemistries

Abstract

The rutting resistances of mixtures that contain polymer-modified asphalt binders with identical performance grades but varied polymer chemistries were evaluated. Eleven asphalt binders were obtained for this study: two unmodified asphalt binders, an air-blown asphalt binder, and eight polymer-modified asphalt binders. Five binders used in a prior study also were included. Asphalt binder properties were measured with a dynamic shear rheometer. Mixture rutting resistance was measured by ( a) the shear modulus, G*, and the Superpave® binder rutting factor, G*/sinδ; ( b) cumulative permanent shear strain (CPSS); ( c) the rut depths from the French pavement rutting tester (French PRT); and ( d) the creep slopes from the Hamburg wheel-tracking device. CPSS and rut depths from the French PRT were the primary mixture tests because they were specifically developed to measure rutting resistance under dry conditions. The high-temperature properties of the 11 asphalt binders had a high correlation to mixture rutting resistance as measured by the CPSSs. A weak correlation was found using the French PRT. Both correlations were high when the data from all 16 asphalt binders and mixtures were analyzed. The number of discrepancies between the high-temperature properties of the asphalt binders and mixture rutting resistance was low. A change in high-temperature performance grade from 70 to 76 significantly increased rutting resistance based on both mixture tests.