Effects of High Temperature on the Interfacial Mechanical Properties of Rubber and Calcium Silicate Hydrate: Nanoscale Insights

Currently, the partial substitution of mineral aggregates with rubber particles in the preparation of rubber concrete (RC) is an effective method for recycling waste rubber materials. However, the mechanism of interfacial interactions in RC at high temperatures is not well understood. This study aims to explore the effect of high temperature on intermolecular interactions at the RC interface and its relationship with macroscopic mechanical properties. Molecular dynamics (MD) simulation technology was employed to construct an RC interface model. The temperature is controlled at room temperature (300 K), medium low temperature (320 K, 340 K, 360 K), and high temperature (500 K, 700 K). The interface model was analyzed from multiple dimensions such as binding energy, turning radius, and interface structure. The results show that the higher the temperature, the more easily water molecules aggregate at the interface of the two phases. As the temperature increases, the proportion of water molecules at the interface increases from 6% to 16%. Since rubber and water molecules cannot form hydrogen bonds, the formation of chemical bonds at the interface between the two phases is affected, leading to a decrease in RC binding energy. The interface bonding energy decreases by 12.6% at a temperature of 700 K. In addition, the radius of gyration of rubber is proportional to temperature. As the temperature increases, the average radius of gyration increases from 5.8 Å to 6.15 Å, and the numerical fluctuation amplitude is greater, resulting in a relatively loose and unstable rubber structure. Furthermore, the bonding strength in RC mainly comes from non-hydrogen bond interactions, and high temperatures cause an increase in bond length while reducing the strength and stability of chemical bonds. Finally, high temperatures increase the atomic movement speed in natural rubber (NR). As the temperature increases, the diffusion coefficients of H_NR and C_NR increase from 0.08 and 0.04 to 1.835 and 1.473, respectively, preventing good connections between atoms at the interface. The study provides nanoscale insights for optimizing RC.