Evaluation of various factors affecting mix design of sulfur-extended asphalt mixes

Several laboratory and field studies from the last five decades, predominantly from the 1970s and 80s, have demonstrated that elemental sulfur is a viable binding material that can be used to partially or fully replace conventional asphalt binder in pavement construction applications. The main goal of this study was to determine and demonstrate the impact of different mix design factors on the performance of sulfur extended asphalt (SEA). These factors include sulfur content, the use of polymer modified versus unmodified base binder, and the method of sulfur addition to the mix. The Hamburg Wheel Tracking test was used to characterize rutting resistance and the Illinois Flexibility Index Test (I-FIT) was used to characterize the cracking performance at both short and long-term aging conditions. Overall, sulfur was found not to compromise the very good rutting resistance of the mix, and optimum binder and sulfur contents were determined based on long term cracking resistance of the mix. It is notable that the optimum binder content did not change when sulfur was used based on the long-term cracking resistance. Results, although with a limited set of materials, demonstrate the feasibility of replacing 30% of asphalt binder with elemental sulfur to produce SEA mixes.