Unraveling disadhesion mechanism of epoxy/CSH interface under aggressive conditions

Almost all FRP-reinforced concrete exposed to the marine environment are susceptible to durability deficiencies due to failure of the FRP/epoxy/concrete interface, especially the vulnerable epoxy/concrete interface, which is frequently attacked by water and ions. Herein, molecular dynamics simulations of epoxy/CSH interface under different environmental exposures are utilized to specifically elucidate the degradation principles of water and ions on the bonding properties and mechanical responses of the epoxy/concrete interface. The environmental sequences associated with the interfacial bonding degradation are arranged as Na2SO4 + NaCl>NaCl>Na2SO4 > Water>Dry. Remarkably, water molecules weaken the interaction between the epoxy and CSH by robbing interfacial H- and Ca-O bonds, thereby reducing the energy barrier to interfacial peel and shear failure. The weakening effects are exacerbated by the presence of aggressive ions, as Na+ ions attracted to the CSH surface accumulate more water molecules in the interfacial region by forming hydrated ions clusters, which ultimately accelerates the epoxy/CSH interfacial degradation.

Automated summary

This study utilized molecular dynamics simulations to investigate the degradation mechanisms of the epoxy/CSH interface under different environmental exposures. It was found that water molecules weaken the interaction between the epoxy and CSH, reducing the mechanical performance of the interface. Additionally, the presence of aggressive ions accelerated the degradation process of the epoxy/CSH interface.