Evaluating effectiveness of WMA additives for SBS modified binder based on viscosity, Superpave PG, rutting and fatigue performance

Addition of Warm Mix Additives (WMA) is expected to cause viscosity reduction and hence could offer lower working temperature. However, it is equally important to study effects of WMA additives on rutting and fatigue behavior of binder. Therefore, the current study aims to investigate rheological characterization of a control SBS polymer modified binder (PMB) with and without WMA additives through different tests such as viscosity, Supepave high performance grade (PG), multiple stress creep recovery (MSCR), linear amplitude sweep (LAS). Three WMA additives namely Sasobit® (wax based) (Wax-S), Rediset® (chemical/surfactant based) (Che-R) and Advera® (water based/ zeolite) (Zeo-A) were used in the present study. The PMB was mixed with three different percentages of Wax-S, Che-R and Zeo-A, thus a total of ten binders were prepared in the laboratory. The results showed that addition of Wax-S and Che-R decreased viscosity of PMB, while addition of Zeo-A increased viscosity of PMB. Wax-S additive was found to bump high PG and enhance rutting and fatigue performance of PMB. Che-R additive degraded high PG and also deteriorated rutting and fatigue performance. Similarly, Zeo-A additive reduced high PG and showed negligible effects on rutting and fatigue performance. The study showed that viscosity might not be considered as a sole criterion for selection of WMA additive. Some WMA additives may decrease viscosity, however, they may also degrade short-term and long-term performance of binders. Thus, a proper caution should be taken while selection of a WMA additive for a type of binder.