Molecular interactions in GO/C-S-H composites: Influence of calcium ions and functional groups

Despite advances in nanomaterial reinforcement, the molecular mechanisms by which graphene oxide (GO) enhances the toughness of calcium silicate hydrate (C-S-H) gel remain unclear, particularly in relation to the role of functional groups and calcium ions. This study investigates the mechanical and structural properties of GO enhanced C-S-H composites using molecular dynamics simulations under tensile and pull-out conditions. The results highlight the crucial roles of free calcium ions (Ca²⁺) and oxidized functional groups in determining interfacial interactions and material performance. Hydroxyl groups significantly enhance tensile strength and Young's modulus, while carboxyl groups improve shear resistance through mechanical interlocking. The study also shows that increasing GO nanosheet proportion of interface area strengthens the composite by enhancing interfacial bonding energy. Furthermore, the migration of a small number of Ca²⁺ ions toward GO nanosheets helps mitigate performance degradation caused by silicate chain damage. These insights contribute to optimizing GO/C-S-H composites for improved mechanical properties, with implications for advanced construction materials.