This paper analyzes the influence of a surfactant warm mix additive on unmodified asphalt’s conventional performance, viscosity-temperature characteristics, surface energy, and spreading performance on aggregate surfaces. The effect of the additive on asphalt’s microstructure was explored by infrared (IR) spectral analysis. The results show the additive has little influence on the penetration, softening point, ductility, and viscosity-temperature characteristics of asphalt; this suggests that the additive does not work by lowering viscosity. The additive can reduce the zero-shear viscosity of asphalt, and adding too much can reduce antirutting performance. The additive also increases the asphalt’s surface energy and the asphalt-water contact angle, while the polar component of surface energy decreases. The additive improves the spreading performance of asphalt on aggregate surfaces and reduces the asphalt-aggregate contact angle; the lower the temperature, the greater the reduction. IR spectral analysis shows that the additive does not react with asphalt—only physical blending occurs. The addition of a surfactant warm mix additive to asphalt allows asphalt mixtures to be more easily mixed and compacted at lower temperatures, thereby saving energy.

Dynamic mechanical analysis (DMA) and other evaluation methods were used to investigate the effect of WS-1, an organic viscosity-reducing temperature mixing agent, on the rheological and conventional properties of warm-mix rubber asphalt (WMRA). The results demonstrated that the WS-1 warm-mix agent exhibited an excellent viscosity-reducing effect and that, with the increasing of WS-1 content, the high-temperature viscosity of the WMRA decreased significantly. The viscosity and softening point of the WMRA increased at 60 °C simultaneously, with the softening point increasing by about 15 °C. The penetration and ductility decreased by about 1 mm and 6 cm, respectively, and the activation energy (Eη) and temperature sensitivity increased. These results indicated that WS-1 could improve the high-temperature performance of WMRA but had an adverse effect on its low-temperature performance. Upon using temperature scanning for the WMRA, the addition of WS-1 significantly increased the rutting factor (G*/sin δ) of the WMRA and greatly improved its rutting resistance within the temperature range examined. The addition of WS-1 changed the viscosity of WMRA, thus affecting the hot-storage stability of WMRA at high temperatures.