Multiscale mechanisms of asphalt performance enhancement by crumbed waste tire rubber: insight from molecular dynamics simulation

The recycling of waste tires is a major environmental problem facing mankind, and the addition of crumbed waste tire rubber (CWTB) to the base asphalt is an extremely promising recycling method. However, the modification mechanism of CWTB to asphalt is not well understood, which restricts the development of CWTB modified asphalt. In this study, the mechanism of CWTB modification of asphalt was explored by dynamic mechanical analysis (DMA), fluorescence microscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and molecular dynamic (MD) simulations. After verifying the asphalt reasonableness using glass transition temperature, CWTB modified asphalt was simulated and experimented. The results showed that CWTB enhanced the high temperature performance of the base asphalt. The microscopic mechanism by which this phenomenon occurs is that CWTB has the largest binding energy with the aromatics (1150–1350 kcal/mol), followed by the saturates (740–830 kcal/mol), followed by the resins (90–330 kcal/mol), and the smallest binding energy with the asphaltenes (100–140 kcal/mol), which causes CWTB to absorb the light components of the asphalt (aromatics and saturates). In addition, the introduction of CWTB reduces the diffusion coefficient of asphalt. In this process, CWTB will gradually swell, which causes CWTB to bind more and more tightly with the base asphalt, and eventually the good high temperature performance of CWTB is transferred to the base asphalt. The macroscopic manifestation of this process is that the rutting factor of CWTB-modified asphalt is significantly higher than that of virgin asphalt. This study can provide basic theoretical support for the application of CWTB-modified asphalt.