Molecular-Scale Study of the Compatibility of Warm-Mix Agents, Rubber, and Asphalt in Warm-Mix Rubber Asphalt

Warm-mix rubber asphalt was analyzed in this study. Based on material characterization test results, a molecular model of warm-mix rubber asphalt was established using Materials Studio software. According to polymer compatibility theory, the molecular compatibility mechanism of warm-mix agents, rubber, and asphalt was studied. The analysis of the binding energy and chemical properties suggested that the warm-mix agents SDYK and EM could effectively augment the interaction strength between rubber and asphalt, thereby enhancing their compatibility. The results of the molecular dynamics simulations and thermal stability, microstructure, and micromechanical property analyses showed that the warm-mix agent changed the glass transition temperature, apparent morphology roughness, adhesion force, and Derjaguin–Muller–Toporov (DMT) modulus of the asphalt. These changes were attributed to the change of the compatibility between various molecules in the asphalt system. The electrostatic potential energy and solubility parameters further demonstrated that the warm-mix agent could improve the compatibility of the rubber asphalt. The difference between the solubility parameters of asphalt before and after adding SDYK was smaller than that after adding EM, indicating that the improvement effect of the SDYK was better. The binding energy of the warm-mix rubber asphalt was positively linearly correlated with the carbonyl index and negatively linearly correlated with the sulfoxide index. The electrostatic potential energy was positively linearly related to the surface roughness. The difference in solubility was negatively linearly related to the adhesion force and DMT modulus, and the correlation was better. This paper presents the interaction mechanism between the warm-mix agents and rubber asphalt at the molecular scale, and the research results can provide some basis for the design and durability evaluation of asphalt materials.