Analysis of thermal susceptibility and rheological properties of asphalt binder modified with microwave activated crumb rubber

Using crumb rubber (CR) as an asphalt modifier not only realizes the recycling of waste tire resources, but also significantly improves the asphalt pavement performance. However, crumb rubber modified asphalt (CRA) prepared by wet process has poor thermal storage stability and microwave activation is an effective way to improve thermal stability. The main purpose of this paper is to compare the temperature susceptibility and rheological characteristics of microwave-activated crumb rubber modified asphalt (MCRA) and CRA. The scanning electron microscopy (SEM) was used to characterize micro morphology of CR particles after various microwave radiation time. The frequency sweep test, multiple stress creep and recovery (MSCR) test, and linear amplitude sweep (LAS) test were conducted and Cole-Cole diagram, Black diagram as well as master curve also were used to analyze rheological properties of modified asphalt. And the modified asphalt segregation experi-ment and solubility were also performed to verify the improvement effect of microwave activation. The results show that microwave activation makes CR surface rough and increases its specific surface area. And the Cole -Cole diagram and Black diagram both show that CR/MCR improve the elasticity of base asphalt, and the elas-ticity of MCRA is lower than CRA, as well as the h value proves that the microwave activation strengthens the polymeric network of asphalt. Solubility and storage stability experiments directly demonstrate that microwave activation can promote the dissolution of CR and reduce the segregation of CR in asphalt. The phase angle master curve is more sensitive to the variation of the internal structure of CRA/MCRA than complex modulus master curve, and the plateau zone in phase angle master curve illustrates the entanglement and interaction within the modified asphalt. The addition of CR/MCR reduce the thermal sensitivity of modified asphalt, and improve high -temperature anti-rutting and medium-temperature anti-fatigue properties. Considering high temperature and fatigue characteristics, the optimal content of MCR in MCRA is 20%-25%.