Twin-Screw Extrusion Desulfurized Crumb Rubber Modified Asphalt: High-Temperature Rheology and Viscoelastic Properties.

To improve the efficiency of waste tire rubber powder modification in asphalt and its high-temperature performance, desulfurized rubber powder with different solubilities was prepared using a twin-screw extrusion process. Desulfurized rubber powder-modified asphalt was then produced using three types of base asphalt, Shell 90#, Zhenhai 90#, and GS 90#, as the base asphalt matrix. Dynamic shear rheometry (DSR), multi-stress creep recovery (MSCR), frequency scanning, Black curves, and complex modulus master curves were used to investigate the effects of rubber powder solubility. We focused on the complex shear modulus (G*), phase angle (δ), rut factor (|G*|/sin δ), creep recovery rate (R), and irreversible creep modulus (Jnr). The results indicate that desulfurization via twin-screw extrusion effectively breaks the sulfur cross-links in the rubber powder, as inferred from the significant increase in solubility, significantly improving rubber powder-asphalt compatibility. Of the three modified asphalts, Shell 90# desulfurized rubber powder-modified asphalt exhibited the slowest decay in high-temperature complex shear modulus, the smallest increase in phase angle, and the best high-temperature rutting factor stability. MSCR tests further confirmed that Shell 90# desulfurized rubber powder-modified asphalt exhibited the highest creep recovery rate, the lowest irreversible creep modulus, and the greatest resistance to permanent deformation. The black curve and the complex modulus master curve confirm that Shell 90# modified asphalt has the best viscoelastic balance and the most stable microstructure. These findings provide a theoretical basis for designing rubber-modified asphalt pavement materials for use in regions with high temperatures and heavy rainfall.