Understanding progressive aging of bitumen-rubber composite binder and its separate phases considering biphase interactions

Bitumen-rubber composite binder (BRCB) has great potential to construct durable road pavement infrastructures that can withstand the environmental aging. However, the aging behavior of BRCB has not been fully investigated so far, especially from the perspective of biphase system with the phase interactions consideration. Therefore, this study investigated the progressive aging behavior of BRCB in terms of separate bitumen phase and rubber phase as well as the biphase interactions, to further understand the mechanisms behind. The results showed that the bitumen phase gradually dominated rheological performance of BRCB with the progressive aging. On the contrast, the fatigue resistance of BRCB was constantly controlled by its rubber phase in the aging process. Secondly, the rubber phase gradually dissolved during the aging with a decrease in the crosslinking density, although the change rate slowed down with the aging duration. The breakdown pattern of rubber structure was further identified as the simultaneous scission of crosslinking bonds and main chains. Besides, biphase interactions during progressive aging primarily included the absorption of light components from bitumen phase into rubber phase and the release of long rubber molecular chains and fillers from rubber phase into bitumen phase. Overall, the progressive aging of BRCBs can be considered as the combined effect of the secondary bitumen-rubber biphase interactions after the first-stage production and thermal oxidation of the bitumen phase.

Graphical abstract