Effects of nano-graphene oxide and ethylene-vinyl acetate rubber powder on mechanical properties and microstructure of mortar

In this study, nano-graphene oxide (GO) and ethylene-vinyl acetate rubber powder (EVA) were used to modify ordinary cement mortar, and the mechanism of the influence of GO and EVA on the mechanical properties of cement mortar was revealed in terms of the chemical composition, pore structure, and microscopic morphology of the materials by using testing methods such as FTIR, XRD, TG, NMR, and SEM. The results indicate that the well-dispersed GO reduces the fluidity of fresh mortar, and this effect could be mitigated by incorporating EVA. The mechanical properties of specimens containing 0.03wt% GO alone were found to be optimal, with a 24.1% increase in compressive strength and a 31% increase in flexural strength at 7 days compared to the benchmark group (PC). Subsequent to the composite infusion of GO and EVA, the 28-day mechanical properties of the resultant specimens exhibit peak values at a GO dosage of 0.03wt% and an EVA dosage of 4wt% weight percent, respectively. Notably, the compressive and flexural strengths recorded are 72 MPa and 12 MPa, demonstrating enhancements of 25.9% and 33.3% when compared to the properties of the PC specimens. The microscopic test outcomes demonstrate that: the nucleation effect of GO accelerates the cement hydration process and can modulate the generation and growth of flower-like hydration crystals, thus refining the pore size distribution of the specimen, and the good filling effect makes the pore structure become denser. The establishment of reticulation film in the early stage of EVA impedes the hydration process of the cement, and in the late stage of hydration, the fully developed reticulation film forms an interpenetrating network with the cement paste, facilitating the pore structure and densification. The cooperative interaction of the two significantly enhances the mechanical properties of the cement mortar.