The influence of graphene oxide on the hydration and mechanical properties of cement-based materials with low water-binder ratio

Graphene oxide(GO) has been used as a functional material in cement-based materials. Most of current research suggests that GO effectively enhance the mechanical properties of cement paste with high water-to-binder (w/b) ratios (0.30-0.50). However, due to the high cost of GO, its use in ordinary concrete materials with high w/b ratios is limited. It has shown promising potential for reinforcement in ultra-high performance cement-based materials with low w/b ratios, such as UHPC. Nevertheless, existing studies have paid limited attention to the effects of GO in cement-based materials with low w/b ratio. This study selected cement-based materials with a w/b ratio of 0.17 as a representative example to investigate the changes in the mechanical properties of hardened cement paste after the addition of GO under different curing conditions. Additionally, by combining the results of microstructural analysis of hydration products, the study explored the mechanism by which GO affects the mechanical properties of cement-based materials with low w/b ratios. The research findings indicate that though an appropriate dosage of GO enhances the compressive strength of cement-based materials with low w/b ratios, it significantly reduces their flexural strength. In addition, GO accelerates the dissolution process of Ca2+ in the early stages, enhancing the degree of cement hydration and increasing the thickness of inner hydration products(IP). This action leads to an increase in the calcium-to-silicate(Ca/Si) ratio and a weakening of the microstructure in outer hydration products (OP). Resultantly, these changes lead to the refinement of small pores and the coarsening of large pores within the hardened cement-based material, collectively manifesting as an improvement in compressive strength and a reduction in flexural strength of the cement paste.