Surface Activation of Wax-Based Additives to Enhance Asphalt Rheological Properties via Rotating Plasma Treatment

Wax-based additives have been widely used in asphalt pavement for their preferable environmental benefits. However, poor compatibility between wax-based warm mix additives and asphalt easily leads to precipitation of wax and cracking of asphalt pavement. Plasma treatment can effectively modify the surface of various materials. This study applies plasma treatment to improve the surface properties of wax-based additives for compatibility improvement in asphalt binder. Compatibility of two different wax-base additives in asphalt binder before and after surface treatment is investigated via cigar tube test and morphology test. In parallel, rheological properties of wax-modified asphalt are characterized from the perspectives of rotational viscosity, rutting resistance, and fatigue performance. Results show the enhanced surface roughness and chemical activity of wax-based additives after plasma treatment. The adhesion between waxes and the asphalt matrix is significantly improved. Waxes within binder are uniformly dispersed after plasma treatment. The incorporation of surface activated wax helps to promote the viscosity reduction of asphalt binder. Furthermore, the high-temperature performance of wax-based asphalt after surface activation treatment of wax is significantly improved, especially for fatty acid amide waxes. As for fatigue performance, plasma treatment improves the fatigue resistance from a compatibility perspective. Therefore, plasma has great promise for facilitating wax-modified asphalt properties from a compatibility perspective.