Influence of crosslink density on the interfacial bonding performance for epoxy resin towards load-induced calcium silicate hydrate gel

Abstract

In epoxy-amine based self-healing cement-based materials, the uncontrollable stoichiometric ratio of both components in the cracks leads to the cured epoxy resin with various crosslink densities. Investigation on the interaction mechanism between cured epoxy resin and C-S-H gel promotes to optimize the final self-healing performances. In this work, the interaction between load-induced broken panels of C-S-H gel and cured epoxy resins with different crosslink densities (e.g., 0.23, 0.77, and 0.97) was studied through molecular dynamic methods. It was found that crosslink density plays an essential role in the geometrical size and atom distributions. Phase separation occurs at the low crosslink density due to the aggregation of amine molecules. The generation of fresh crosslink points limits the free motion of epoxy molecules with higher crosslink density. Meanwhile, the cured epoxy resin with higher crosslink density causes a high porosity in the interfacial region between the epoxy resin and C-S-H gel substrates, degrading the mechanical performance of materials.