Study on aging mechanism of SBS/SBR compound-modified asphalt based on molecular dynamics

Abstract Component ratio change is considered to be the main reason leading to the deterioration of asphalt properties, but there are few studies on the aging mechanism from the perspective of modifier molecules. To reveal the aging mechanism of styrene–butadiene–styrene block copolymer (SBS)/styrene butadiene rubber (SBR) compound-modified asphalt, the micro mechanism in the aging process was studied by combining molecular dynamics (MD) and Fourier transform infrared spectroscopy (FTIR). First, MD was used to establish the micro models of SBS/SBR compound-modified asphalt at different aging stages (non-aging, short-term aging, and long-term aging) and to verify its rationality. Second, the micro characteristics of the SBS/SBR compound-modified asphalt micro model, such as solubility parameters, diffusion coefficient, interface interaction energy, and radial distribution function, were analyzed by calculation. Finally, the FTIR results proved the rationality of the simulation and explained the aging mechanism of SBS/SBR compound-modified asphalt. The results show that the cohesiveness density and solubility parameters of SBS/SBR compound-modified asphalt increase, the diffusion coefficient decreases, and the molecular interface stability increases during the aging process. And, the carbonyl index, sulfoxide index, and aromatic ring index increased in different degrees after aging. The study explains the aging mechanism of SBS/SBR compound-modified asphalt from the perspective of modifier molecules and provides a theoretical basis for the research of asphalt anti-aging.