Properties investigation of the SBS modified asphalt with a compound warm mix asphalt (WMA) fashion using the chemical additive and foaming procedure

Styrene-butane-styrene (SBS) modified bitumen has been widely applied in pavement engineering due to its excellent cracking and rutting resistance. However, there are workability concerns due to its higher viscosity compared to virgin bitumen. Conventional Warm Mix Asphalt (WMA) technologies including surfactants and foaming additives have been successfully applied to SBS bitumen. This study attempts to evaluate whether compound WMA technologies (e.g., the foaming procedure and the surfactant additive) can bring further engineering and environmental benefits. Surfactant additive solution (Evotherm-DAT) was used as a novel foaming agent to foam SBS bitumen instead of water during the foaming process. A series of chemical, foaming and rheological tests were conducted for performance evaluations on the surfactant additive (SA) foamed SBS bitumen. It was found that a limited chemical reaction happens among SA and SBS bitumen. Besides, surfactant used as the novel foaming agent can bring positive effects on foaming behaviors. Furthermore, SA foamed SBS bitumen presents better workability, rutting and fatigue resistance. Finally, it is proven that the compound WMA fashion using surfactant additive and foaming procedure is feasible on SBS bitumen.