Modification of the Crumb Rubber Asphalt by Eucommia Ulmoides Gum under a High-Temperature Mixing Process

The crumb rubber (CR) asphalt has some defects of high viscosity and poor storage stability, which brings great challenge to the high-quality construction of the CR asphalt pavement. To improve the interaction between the CR and base binder, the Eucommia ulmoides gum (EUG) with double-bond structure similar to trans-polyoctenamer rubber (TOR) was used to modify the CR asphalt. However, the original EUG double bond is basically inactive at room temperature and cannot form the effect of TOR. Open double bonds of EUG with asphalt and rubber powder form a network structure similar to TOR-modified rubber asphalt by high-temperature mixing with EUG in a torque rheometer. The effects of modified CR on rubber asphalt were analyzed by macro- and micro-experiments such as rotational viscosity tests, segregation tests, FTIR tests, and PG tests. It was found that the high-temperature mixing process works in both physical and chemical ways to mix the CR and EUG into an inseparable substance. The modified CR has higher chemical activity after desulfurization and degradation, which allows it to form a more effective chemical connection with asphalt. EUG can build a stable spatial crosslinking structure in CR asphalt due to the sulfurization reaction, which significantly improves the construction workability and system stability of the CR asphalt.