Evaluating the thermal and mechanical properties of GO-modified epoxy/C–S–H interface: an atomic investigation

Modifying epoxy resin with carbon nanomaterials is one of the promising methods to improve the fiber-reinforced polymer (FRP)/concrete interfacial properties, and such manipulation first requires comprehensive understanding of the bonding mechanism between the modified epoxy resin and the concrete matrix. In this paper, the interfacial bonding properties between epoxy resins modified by graphene oxide (GO) nanosheets and calcium silicate hydrate (C–S–H), the main bulk phase of concrete, are investigated using molecular dynamics simulation. At the molecular level, the GO-epoxy/C–S–H interface is constructed, and the mechanical behaviors of the interfacial system are simulated at elevated temperatures (from 298.15 to 433.15 K). Results show that the GO modification significantly enhances the mechanical resistance of the epoxy/C–S–H interface, as evidenced by the increase in the pulling force threshold of ~ 20%. Analysis reveals that the polar groups on the GO surface strengthen the interfacial ionic and structural hydrogen bonds, thus improving the bonding integrity of the epoxy/C–S–H interface. At elevated temperature levels, the high thermal stability of the GO-epoxy molecule, as well as its low energy loss with the C–S–H matrix, is the main driver for the enhanced thermal and mechanical properties of the epoxy/C–S–H interface.