Evaluating the Efficiency of SMA Mixtures Containing Crumb Rubber and WMA Additives

Abstract

The huge amount of waste tire deposit and its adverse influence on the environment is a serious global concern. Using crumb rubber (CR) as a bitumen additive not only improves the efficiency of asphalt mixtures but also reduces ecological concerns. The increase in production temperatures is the negative influence of CR on asphalt mixtures. Warm mix asphalt (WMA) additives are a good solution for this problem; they can diminish production temperatures by around 30°C. This research aims to examine the characteristics of CR-modified stone matrix asphalt (SMA) mixtures containing WMA additives. Three CR contents (5%, 10%, and 15% by weight of bitumen) and two kinds of WMA additives (Sasobit and Zycotherm) were considered for this purpose. Tensile strength ratio, wheel tracking, dynamic creep, and resilient modulus tests were used to investigate the potential of moisture damage, rutting resistance, and stiffness modulus of SMA mixtures. It was found that regardless of the additive type, increasing the CR content led to the optimum binder content, dry indirect tensile strength, resilient modulus value, and flow number value increase. Still, the wet indirect tensile strength and rut depth decreased. Furthermore, using WMA additives led to a decrease in production temperatures. Also, it was found that among all specimens, the samples containing Zycotherm had better moisture resistance.