Graphene oxide coated fly ash for reinforcing dynamic tensile behaviours of cementitious composites

By virtue of its low cost, high workability, wide availability and suitability for large-volume fabrication, cementbased grouting is the most applied material in underground projects. However, due to the weak tensile strength and high-frequency impact dynamic load disturbance in underground engineering, cement-based grouting is vulnerable to tensile damage, seriously influencing the stability and safety of underground projects. Hence, in this work, the graphene oxide (GO) coated fly ash was adopted to reinforce the dynamic tensile behaviour of the cement-based matrixes to fabricate high-performance, cost-effective and environmentally friendly cementitious composites. The test results show that the GO-coated fly ash could significantly enhance the dynamic tensile performance of the cementitious composites. With only 0.08 wt% GO mixing, the dynamic tensile properties can be strengthened by 19.5-88.5%. After GO nanosheets accelerate the cement hydration process and improve the chemical composition of hydration products, GO nanosheets exhibit macroscopic nucleation and "crack-bridging" effects on the cement matrixes, and the cracks propagation of the hardened specimens would be suppressed under dynamic loading, thus enhancing the tensile resistance of the specimen. The fractal dimension calculation results prove that the GO-coated fly ash-modified cementitious composites have higher integrity after tensile impact, about 2.8-11.9% higher than plain cement-based slurry. Finally, the theoretical analysis reveals that GO nanosheets can enhance the tensile behaviours of the cement matrix by optimizing the dynamic load coefficient. Nevertheless, with the crack propagation, the reinforcing efficiency of GO would be gradually weakened. The findings of this study can promote an understanding of the enhancing mechanisms of GO on the dynamic tensile behaviour of cementitious composites and inspire the potential application of GO-coated fly ash to reduce cement usage in grouting engineering.