Effects of water and ions on bonding behavior between epoxy and hydrated calcium silicate: a molecular dynamics simulation study

The bonding performance between epoxy resin and cement-based materials affects the load transfer capacity between fiber-reinforced polymers (FRP) and concrete. FRP-reinforced concrete structures are inevitably exposed to aggressive environments during service, triggering interfacial deterioration and premature structural failure. To assess the stress state of FRP-reinforced concrete structures and to predict their long-term durability, a fundamental investigation of the bonding performance of the epoxy/concrete interface in aggressive environments is required. In this study, the bonding performance between epoxy resin and calcium silicate hydrate (CSH) in water and salt environments is investigated using molecular dynamics (MD) simulations. The adhesion energy of epoxy/CSH interface calculated via combine MD simulation and Bell’s model theory is dramatically reduced in water and salt environments. Analysis of the static structures and dynamic properties reveals that the adhesion between the epoxy resin and CSH matrix is mainly dependent on the O–Ca–O and H-bond connections, while the water and salt environments significantly weaken these connections and disrupt the integrity of the epoxy/CSH interface. This study provides a molecular-level understanding of the bonding degradation at the epoxy/CSH interface in aggressive environments. Graphical abstract This study provides a molecular level understanding of the bonding degradation between epoxy and CSH matrix in aggressive environments.