The research for structural characteristics and modification mechanism of crumb rubber compound modified asphalts

•The lack of physical properties of CRM asphalt was pointed out.•The way for improving the physical properties of CRM by using SBS or sulfur was provided.•The effect of SBS and sulfur on the structural characteristics of CRM asphalt before and after ageing was studied carefully.•The major ways for studying the structural characteristics of CR compound asphalt were displayed fully.

The crumb rubber (CR) compound modified asphalt with improved tenacity and high- or low-temperature properties was prepared by the addition of styrene–butadiene–styrene (SBS) and the stability of CR/SBS-modified (CRSM) asphalt was improved by the addition of sulfur. Rheological testing demonstrated the improved high-temperature performance of modified binders and indicated the susceptibility of vulcanizated binder to dynamic shear. Morphology observation showed the compatibility between CR and asphalt was improved greatly by vulcanization or ageing. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) analysis showed the characteristics and distribution of the major functional groups of modified asphalt before and after ageing. In thermal analysis, DSC curve showed the effect of ageing and modifier on the molecule weight distribution and constituents of asphalt. The thermal stability and susceptibility of each binder to thermal decomposition were evaluated by using TG and DTG curves, which indicated the structural characteristics of binder and demonstrated the conclusion drawn by DSC analysis further.