Multilevel Analysis of the Aging Mechanisms and Performance Evolution of Rubber-Modified Asphalt

Rubber powder is widely used to modify base asphalt binder to improve the low-temperature performance and crack resistance of asphalt mixtures. This paper investigates the aging mechanism and performance evolution of rubber-modified asphalt in terms of three levels: rubber powder, rubber-modified asphalt, and rubber-modified asphalt mixture. The multilevel analysis results show that mass loss, phase transition, and melting occur during the process of rubber powder aging, and scanning electron microscope images indicate that the surface morphology of the rubber powder becomes smoother. The aging of base asphalt leads to the volatilization and oxidation of light components, resulting in the production of carbonyl and sulfoxide groups and a reduction in the swelling between the rubber powder and aged base asphalt. The aging of rubber powder leads directly to a significant decrease in the modification effect of the rubber; thus, rubber powder aging plays a more decisive role in the degradation of rubber-modified asphalt than base asphalt aging. By contrast, the performance indicators of aged rubber-modified asphalt are able to reach their highest values due to the effective blending between the rubber powder and base asphalt, which results in an enhanced antiaging capability. The sensitivity of all performance indicators of rubber-modified asphalt to the aging temperature is relatively low, except for the 5 degrees C ductility index. Therefore, the mixing temperature needs to be strictly controlled to a specified value when rubber-modified asphalt is applied in cold areas that require low-temperature stability of the mixture. As for the aged rubber-modified asphalt mixture, the dynamic stability improved significantly, the ultimate tensile strain at low temperature decreased, and the antifatigue performance decreased to different extents under different stress ratios.