Comparative analysis of rubber/cementitious interface enhanced by multiple modifying agents in rubber concrete - experimental and molecular dynamics studies

Rubber concrete (RUBC) is an innovative eco-friendly material, but its weak internal interfaces and pores lead to reduced mechanical properties. This study compares the modification effects of ethylene-vinyl acetate copolymer (EVA), nano-calcium carbonate (Nano-CaCO3), and silane coupling agent (KH560) on the rubber-cement interface in RUBC to improve its mechanical properties. Macroscopic tests showed that all three modification methods improved RUBC’s compressive, shear, and flexural properties to varying degrees. Under the same conditions, RUBC modified with KH560 and Nano-CaCO3 outperformed EVA-modified RUBC in terms of mechanical performance. Microscopic tests (SEM, XRD, FTIR) indicated that KH560 and Nano-CaCO3 significantly increased cement gel formation, with KH560 notably enhancing the rubber-cement interface bonding. Molecular dynamics simulations showed that EVA, Nano-CaCO3, and KH560 increased interaction energy at the interface by forming more hydrogen bonds. However, KH560 formed stronger chemical bonds with C-S-H gel through Si-O-Si bonds. This study provides experimental and theoretical support for engineering applications aimed at enhancing RUBC’s mechanical properties through multiscale analysis.