Properties and interaction evolution mechanism of CR modified asphalt

•Thermo-mechanical aging is an effective way to perform CR degradation.•Increased degradation of CR improves its compatibility with asphalt.•The evolution mechanism of interaction among CR modified asphalt was obtained.•The substance exchange in CR modified asphalt is examined by morphology, Tg and Zn element tracing. With the aim of understanding the influence of crumb rubber (CR) degradation degree on the properties of CR modified asphalt and the modification mechanism, CR with varying degradation degree was obtained through thermo-mechanical and thermal aging method. Subsequently, CR modified asphalts were prepared using the conventional wet process. The degradation degree of CR was evaluated by measuring gel contents and crosslinking density, and the results show that degree of CR thermal degradation is more effective with the assistance of mechanical force. The mechanism of CR degradation entails the breaking and forming of C-S and S-S, with the former being more sensitive to lower temperatures while the latter predominating at higher temperatures. Along with the increasing degree of CR degradation, the thermal storage stability, low-temperature properties and workability of modified asphalts can be improved, albeit at the expense of resistance of rutting and fatigue. The evolution mechanism of interaction among CR modified asphalt was thoroughly examined, considering surface properties, thermal behavior, morphology, trace analysis of Zinc (Zn) elements and rheological responses. The results indicate that the interaction mechanism among CR and asphalt occurs via the wetting effect of asphalt on CR firstly, followed by the substance exchange between each other, and the interaction can be enhanced by the degradation treatment of CR.