Investigation of rheological properties and modification mechanism of SBS-modified asphalt with different warm mix additives

The application of warm mix asphalt (WMA) technology in polymer-modified asphalt becomes increasingly widespread, but it lacks thorough investigation on the interaction mechanism between warm mix additives and polymers. Accordingly, two new warm mix additives, an organic viscosity-reducing modifier (A) and a surfactant-based modifier (C), were selected to prepare the warm mix SBS-modified asphalt. The basic properties, viscosity-temperature characteristics, ageing resistance and rheological properties of modified asphalt were tested. At last, the modification mechanism was elucidated through a series of microscopic tests. The results indicated that A could more effectively enhance the construction workability of SBS-modified asphalt, while C had little effect on its basic properties. Both new modifiers, especially A, reduced the high-temperature property of asphalt, with partial recovery after short-term ageing. The microstructure test results indicated that the two modifiers were physically modified with SBS-modified asphalt. Both additives improved the dispersion uniformity of SBS particles in asphalt, and the microscopic morphology parameters obtained from quantitative analysis reflect the macroscopic properties of asphalt. Moreover, the light components and rubber powder of A improved the flexibility of asphalt, and C enhanced its low-temperature performance, which demonstrated that these two modifiers were more suitable for asphalt pavements in cold regions.