▎ 摘　　要

This study aims to improve the fracture properties of cementitious materials by adding graphene oxide (GO) and graphene oxide-silica nanocomposites (GO-nanoSiO(2)). The pristine GO was coated with nano-silica to form GO-nanoSiO(2) composites. Based on the three-point bending test, the fracture toughness and fracture energy of cementitious materials were calculated to provide comprehensive fracture mechanics characterization. The fracture surface morphology and the crack development in mortar were detected by ultra-depth microscopy and scanning electron microscopy. The results demonstrate that the addition of GO-nanoSiO(2) is more beneficial to improve the fracture properties of cementitious materials than pristine GO and the amount of nano-silica grafted on GO surface affects its enhancement effect. The initial fracture toughness, unstable fracture toughness and fracture energy of mortar reinforced by GO-nanoSiO(2) (0.05 wt% GO and the mass ratio of nano-SiO2/GO is 2.8) are increased by 92.2%, 64.7% and 77.5%, respectively. GO-nanoSiO(2) improves the roughness of mortar fracture surface, changes the propagation mode of cracks, and makes the crack propagate along a more tortuous path which contributes to energy dissipation.