Study on viscosity reduction mechanism of warm-mixed rubber modified asphalt: A green sustainable perspective

Owing to the large viscosity and mixing temperature of crumb rubber modified asphalt (CRMA), possesses high construction costs, the addition of warm-mix agent can reduce the viscosity and mixing temperature of CRMA. In this study, the Sasobit or DWMA-1 warm-mix agent was added into CRMA to prepare the warm-mix crumb rubber modified asphalt (WRMA). Rotational viscosity (RV) measurement revealed that viscosity of WRMA reduced significantly with the increasing temperature. Dynamic shear rheometer (DSR) showed that Sasobit and DWMA-1 have similar effects on the viscoelasticity of WRMA at the actual pavement temperature (64 °C). Phase separation test showed that the addition of warm-mix agent enlarged the softening point difference, and DWMA-1 had better anti-segregation effect than Sasobit. Fourier transform infrared spectroscopy (FTIR) analyses revealed that there was a chemical reaction after mixing the warm-mix agent and produced new functional groups at 1368 cm⁻¹∼735 cm⁻¹. Fluorescence microscope (FM) and polarizing microscope (PM) analyses indicated that warm-mix agents could improve the solubility between rubber and asphalt. DWMA-1 had a lesser impact on the surface roughness of WRMA compared to another warm-mix agent or composite agent. In addition, preparation method and viscosity reduction mechanism of WRMA was elaborated. This study could be of potential interest for engineering applications of WRMA.