Mechanical properties and microstructure of graphene oxide cement-based composites

•Studying the combined effect of GO content and w/c ratio on GO-cement composites.•Exploring the influence of GO on the optimal water/cement ratio.•Studying the governing mechanism for the improvements in GO-cement composites.•Investigating the composition-microstructure-strength relationship for GO-cement. Aiming to improve the flexural and compressive strength of cement, graphene oxide (GO) was incorporated into the production of cement-based composites in this study. The effects of the GO content and water/cement (w/c) ratio on the mechanical properties and microstructure of GO–cement composites were systematically investigated through experimental tests. Testing results show that with a constant w/c ratio, the flexural and compressive strengths of the developed GO–cement composites increased first and then declined with respect to the increase in GO content. Specifically, the increase in flexural strength was more significant than that in compressive strength, indicating that the addition of GO could help improve the toughness of cement composites. Additionally, a combination of a w/c ratio of 0.35 and a GO content of 0.05 wt% led to both the highest flexural and compressive strengths. The investigation of the composition–microstructure–strength relationship shows that the introduction of GO could help improve the macroscopic properties for the cement-based composites via improving the microstructure of cement hydration products, refining the crystal size, and forming a denser and more uniform network structure. The filling effect, hydration effect and nucleation effect of GO could be optimized with an appropriate combination of w/c ratio and GO content.