Silane Coupling Agent Modification Treatment to Improve the Properties of Rubber–Cement Composites

Declining strength is a key limitation for the promotion and application of rubber–cement-based composites. Silane coupling agents (SCAs) provide a new idea for improving the weak interface of rubber–cement-based materials, but the mechanism of SCA modification in the improvement of mechanical properties is not well established. In this paper, for the first time, a multi-scale exploration of SCA-modified rubber–cement-based materials was conducted to explore the modification effect and to reveal the modification mechanism using a combination of experiments and simulations. The experimental results showed that the mechanical properties of KH570-modified rubber–cement-based composites were greatly improved as compared with the composites treated with KH550, KH560, and A151. The modification treatment can effectively introduce KH570 molecules into the weak interface, thus effectively repairing the interfacial defects between the rubber particles and the cementitious material. The molecular dynamics simulation results show that the weak intermolecular interaction between the butadiene group of butadiene rubber and the calcium–silica structure of C–S–H is the essence of the weak combination of the two phases. The mechanical occlusion between KH570 molecules and rubber molecular chains can effectively bond the elastic rubber to the hard cement matrix, improving the frictional resistance and chemical bonding at the interface and giving it full play in the excellent deformation properties of rubber when the composite material is stressed.