Preparation and modification mechanism study of microwave-treated crumb rubber and waste engine oil-modified asphalt

The objective of this study was to characterize the performance of waste engine oil (WEO) and microwave-treated crumb rubber (CR)-modified asphalt (WEO-MCRA) and analyze the modification mechanism. The viscosity and dynamic shear rheological (DSR) tests were carried out to evaluate the viscoelasticity property of WEO-MCRA. The storage stability and fluorescence microscope (FM) tests were used to characterize the compatibility of the components. The Fourier transform infrared spectroscopy (FTIR) and molecular dynamic simulation were introduced to analyze the change of function groups and modification mechanism. The results demonstrated that introducing Wt.20% CR treated with microwave and Wt.6% WEO obtained a lower viscosity, excellent storage stability, and satisfactory elasticity properties of asphalt. The morphology of modifiers presented a thread-like structure microscopic with the range of WEO content Wt.3%-Wt.6%. Molecular dynamic simulations revealed that the aromatic may be intensively absorbed by CR and increase the likelihood of phase separation. WEO reduced the binding energy of CR to aromatic from 178.0 to 151.5 kcal/mol, which will contribute to the disaggregation of CR clusters. The diffusion coefficient shows a more obvious decrease with the addition of WEO and microwave treatment, which will benefit the stability of the asphalt. This study can provide a reference for the recycling of CR and WEO.