Evaluating Surfactant-Foamed Warm Reclaimed Asphalt and Its Blending Efficiency

A compound warm-mix asphalt (WMA) technology, surfactant-foamed asphalt (SFA), was proposed to promote warm-mix reclaimed asphalt pavement technology and provide engineering and environmental benefits through nonrenewable materials recycling, cost saving, and energy and emissions reduction. The blending efficiency is critical for the design of SFA warm-mix reclaimed asphalt pavement (SFA-WMRAP) incorporating higher levels of RAP. This study investigated the blending efficiency of virgin and aged asphalt in SFA-WMRAP containing high RAP content. First, the effects of foaming temperature and foaming-surfactant additive dosage on the foaming characteristics and rheological properties of SFA were investigated, and the optimal foaming conditions were determined. Next, an atomic force microscope (AFM) test and fluorescence microscopy (FM) test were used to quantify its blending efficiency after using the stage extraction method. Results indicated that SFA under optimal foaming temperature and surfactant content achieved better workability, rutting resistance, and fatigue resistance. SFA-WMRAP with high RAP content showed a similar blending efficiency compared with the hot-mix process by using the gray mean value as an evaluating index, exhibiting great potential to promote WMRAP for incorporating high contents of RAP.