Comparative Performance of Unmodified and SBS-Modified Asphalt Mixtures Made with Blowdown (CarSul) and Calcium Carbonate as Mineral Fillers

Abstract

This research aims to find a cost-effective way to mitigate the environmental problems caused by waste disposal, and Iraq is struggling to deal with the growing problem of rising solid waste creation and declining landfill capacities, such as blowdown, a carbon-sulfur by-product material of sulfur purification. This study evaluated the effects of blowdown [carbon-sulfur (CarSul)] as a mineral filler on both unmodified and styrene-butadiene-styrene (SBS)-modified asphalt mixtures as potential calcium carbonate (CaCO3) replacement. Performance tests and parameters were conducted, and the results were analyzed statistically using Minitab software. The results showed that using blowdown for unmodified and SBS-modified asphalt mixtures as a filler replacement led to improve Marshall stability, indirect tensile strength, deformation strength, Marshall quotient, and semicircular bending test parameters, such as maximum load, total fracture energy, and critical J-integral, compared with the mixtures with CaCO3 filler. This provides advantages such as improved cracking and rutting resistance while meeting the requirements for Marshall characteristics and moisture susceptibility, indicating that using blowdown as a mineral filler in asphalt mixtures can potentially lead to cost savings and conserve valuable landfill space while also improving asphalt mixtures’ performance. Furthermore, the analyses of test results show that the performance of SBS-modified asphalt mixtures is significantly better compared with unmodified mixtures, reducing the temperature susceptibility and improving the rutting and cracking resistance.