Enhancing water resistance and stability of CFRP/concrete interfaces with silane coupling agents: Insights from nanoscale investigations

• The water resistance and stability of CFRP/concrete interfaces under hydrothermal conditions were systematically evaluated. • Silane coupling agents significantly improved adhesion, reducing atomic diffusion and enhancing durability. • The study divided the wetting process into three stages, elucidating temperature effects on adhesion performance. The durability and performance of CFRP/concrete structures are critically dependent on the integrity of the epoxy/concrete interface in hydrothermal environments. However, the degradation mechanisms of these interfaces under varying temperature conditions remain underexplored. This study explores the water resistance and stability of epoxy/concrete interfaces under hydrothermal conditions using molecular simulations. The research focuses on how temperature impacts molecular diffusion, hydrogen bonding, and the integrity of the composite interface. Findings reveal that higher temperatures increase the molecular kinetic energy, leading to greater water molecule infiltration and degradation of the interface. Modification with γ-amino-propyltriethoxysilane (SCA) improves adhesion and stability, especially at extreme temperatures, demonstrating the protective effect of SCAs on the C-S-H gel. The study divided the wetting process into three stages: initial adsorption, mixing, and sustained dissociation/stability. At 253 K, the SCA-modified epoxy maintained a stable attachment to the C-S-H substrate, while at 313 K, the modified resin showed enhanced adhesion, increasing the adhesion rate from 17 % to 60 %. The research highlights the protective effect of silane coupling agents on the C-S-H gel, promoting better bonding and reducing atomic diffusion on the surface. The findings provide a theoretical basis for enhancing the durability of CFRP/concrete structures in the hydrothermal environment.