Properties of Asphalt Binders with Increasing SBS Polymer Modification

The properties of several asphalt binders with gradual styrene-butane-styrene (SBS) polymer modification were studied. The base binders used were straight-run PG 52-34, 58-28 and 64-28 which were modified with polymers at concentrations of 0, 1, 2, 3 and 4%. Two types of SBS polymers were used with different grain sizes and they were integrated into the binder with the same cross-linking agent. The rheological properties were studied using a Dynamic Shear Rheometer (DSR) with Temperature-Frequency Sweep Master Curves and the Multiple Stress Creep Recovery (MSCR) Test. The Master Curves showed that the polymer modification, up to 4% addition, increases the binder stiffness at high temperatures, which is a good indication of improved rutting resistance. The MSCR test showed improved percent recovery and compliance with increasing concentrations of SBS. To observe the effects of polymer addition on a microscopic level, the unaged binders were analyzed with the Environmental Scanning Electron Microscope (ESEM), finding that there were no significant changes with the level of polymer addition.