Molecular insights into the performance of epoxy/CSH interface under coupled hygrothermal environment and tensile load

Abstract The durability of epoxy/calcium silicate hydrate (CSH) interfaces is critical in the reinforced concrete structures under coupled hygrothermal and tensile load. However, the degradation mechanism of the interface in the conditions remains incompletely understood. This study used the molecular dynamics (MD) simulation to investigate the effects of hygrothermal environment on the atomic distribution, interfacial energy, tensile behavior, and failure mechanisms of the epoxy/CSH interface. The results revealed that the increased water content reduced the atomic penetration and adsorption, raising the interfacial energy and weakening the bonding strength of the epoxy/CSH interface. When the water content of the interface increased from 0% to 12% at 298K, the peak tensile load decreased by 31.11%. When the temperature of the interface increased from 298K to 368K with the water content of 6%, the peak tensile load decreased by 18.91%. It demonstrated that the humid condition accelerated the interfacial debonding due to a lubricant effect of the water molecules. This work provides molecular-level insights into the degradation mechanism of the epoxy/CSH interface, offering guidance for enhancing the durability of epoxy-based reinforcement systems in harsh environments.