Effects of WMA Technologies on Asphalt Binder Blending

Abstract

Because of environmental and economical benefits, the paving industry has made attempts to incorporate recycled asphalt pavement (RAP) or recycled asphalt shingle (RAS) into warm mix asphalt (WMA). However, the low temperatures at which WMA is produced may affect the virgin-recycled binder blending in RAP/RAS mixtures. In this study, a lab testing procedure was developed to evaluate the effects of WMA technologies on binder blending. The results from the study showed that WMA additives, including sasobit, rediset, cecabase, and evotherm, slightly decreased the viscosity of the asphalt binder at 135°C. However, control binder tested at 165°C showed significantly lower viscosity than WMA binders. This may raise the concern over workability of nonfoaming WMA mix. WMA additives yielded higher blending ratio than control mix produced at 135°C, but hot mix asphalt (HMA) produced at 165°C still showed the highest blending ratio value. This indicates that a concern still exists over asphalt blending even if WMA additives are used. Foaming technology yielded a higher blending ratio, indicating that foamed WMA may yield a higher blending than regular HMA. It was also found that temperature is critical to blending in RAS mixture. Finally, the mix produced with coarse virgin aggregates and medium RAP may not be sensitive enough to test the effect of WMA additives on blending, whereas the mix with medium virgin aggregates and fine RAP was more effective.