Influence of nanosheet size and oxygen-containing functional group content on the reinforcing efficiency of graphene oxide on cementitious composites

Abstract

Dispersion is crucial in the reinforcement efficiency of graphene oxide (GO) in cementitious composite modification. However, the generally used nanomaterial dispersion methods commonly affect the physical size and functional group proportion of GO, thus weakening the reinforcing effects of the cement reinforcement. In the present study, the molecular dynamical (MD) simulation was employed to investigate the tensile mechanical properties of calcium silicate hydrate (C–S–H)/GO composites under different physical sizes and oxygen-containing functional group contents of GO nanosheets. The results demonstrate that the mixed GO nanosheet reinforces the C–S–H via ductility and strain energy density reinforcement from the MD perspective rather than a macroscopic peak strength improvement. Benefiting from the crack-bridging roles of GO, the ductility and strain energy density of C–S–H composites can be strengthened by up to 53.6–66.7%. A new "danger interval" mechanism is found in GO modification cementitious composites. With an increment of the physical size and oxygen-containing functional group content of inserted GO, the peak stress, ductility, and strain energy density of the GO/C–S–H composites all demonstrate a first declining and then rising trend, hitting the lowest value at 0.18 oxygen–carbon ratio and 0.48 size ratio with C–S–H in the z-axis direction. The tensile strain and stress characteristics further illustrate that inadequate nanosheet size and oxygen-containing functional group content weaken the ability of strain/stress redistribution capability of GO, thus limiting the reinforcement efficiency of the GO. The findings of this study would not only board the reinforcing mechanism of GO in cement-based materials but also guide the reasonable GO-reinforced cementitious composite manufacture in the future practical engineering.