Rutting, thermal cracking, and stripping are among the most severe distress types in asphalt pavement. In this study, a specified type of styrene-butadiene-styrene (SBS) was used as a modifier for a low viscosity asphalt binder G80/100 (PG 58-22) to overcome the issues of the distresses in the asphalt mixture. The mixing process had been evaluated by using fluorescent microscopy. The control- and SBS-modified binders were subjected to all conventional and Superpave binder tests. The Hamburg wheel tracker (HWT) and indirect tensile strength ratio (ITSR) tests were conducted to evaluate the engineering properties of the control and modified asphalt mixtures. The used SBS percentages were 1, 2, 3, 4, and 5% of the total weight of the binder. The results showed lower penetration, higher softening point, viscosity, and elastic recovery. The dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests showed an increasing SBS% leading to an increase in both values of high and low temperatures of the asphalt performance grade (PG). The tensile strength ratio and Hamburg wheel tracker tests’ results showed that the highest TSR and rutting parameter values were obtained at 3% SBS, which was the optimum SBS content for the asphalt mixture and the resulted modified asphalt is PG76-16.

The most severe distresses in asphalt pavement are rutting, fatigue, and low-temperature cracking; therefore, to solve these problems, it is essential to modify asphalt binders in asphalt concrete mixtures. In this study, a comparison between using styrene-butadiene-styrene (SBS) and crumb rubber (CR) as modifiers for asphalt binders to overcome distress issues was conducted. Base and SBS or CR-modified binders were subjected to all conventional and Superpave binder tests. Engineering tests such as the Hamburg wheel tracker and indirect tensile strength ratio were also run to evaluate the engineering properties. The used SBS percentages were 1, 2, 3, 4, and 5%, while CR percentages were 3, 6, 9, 12, and 15% by total weight. The results showed lower penetration, higher softening point, viscosity, and elastic recovery for both additives. In addition, dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests showed increasing values of both high and low temperatures of modified asphalt performance grade (PG) with increasing SBS or CR percent. The tensile strength ratio and Hamburg wheel tracker results showed the best engineering properties at 3% SBS or 9% CR, the optimum percent. A triple percentage of CR is needed to get the same effect of SBS for the asphalt mixture.

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