Plasma Surface Treatment of Waxes to Enhance the Compatibility and Performances of Wax Warm-Mix Asphalt

Abstract

Wax warm additives are widely used in asphalt mixture production due to their energy savings and low cost. However, the compatibility problem between waxes and asphalt binders leads to wax precipitation and asphalt low-temperature cracking. Plasma treatment technology can modify the surface of waxes. In this study, plasma technology was used to modify Fischer Tropsch (FT) wax surfaces, linear aliphatic hydrocarbon wax, and two plastic cracking waxes. The effects of waxes on the high-temperature performance, fatigue performance, low-temperature physical hardening, and wax precipitation temperature of asphalt binders were evaluated by the multistress creep recovery (MSCR) test, linear amplitude sweep (LAS) test, extended bending beam rheometer (ExBBR) test, and dynamic shear rheometer (DSR) viscosity test. In addition, the effect of plasma treatment on waxes in terms of low-temperature physical hardening and wax precipitation temperature was explored. The results showed that the effect of waxes on the high-temperature properties of asphalt binders was related to wax type, dosage, and stress level. Within the allowable dosage range, waxes improve the fatigue properties of asphalt binders. After plasma treatment, the surface roughness and activity of waxes were increased, resulting in the alleviation of physical hardening of waxed asphalt binders and a decrease in wax precipitation temperature. Among them, plastic cracking waxes were more sensitive to the plasma treatment technique.