Enhancing the pozzolanic effect and mechanical properties of fly ash cement using graphene oxide

The incorporation of fly ash (FA) as an admixture to partially replace cement clinker can improve the strength of cement pastes. However, the addition of FA leads to weak early-age mechanical strength. Graphene oxide (GO) is an ideal two-dimensional material that can be functionalised on FA surfaces and accelerates cement hydration kinetics through oxygen-containing group-mediated Ca2+adsorption, which synergistically enhances the dissolution of FA and subsequent pozzolanic reactions. This study clarifies the mechanism of enhancing the pozzolanic activity of FA in the cementitious system by introducing 0.05% GO. The results confirmed that the incorporation of GO significantly enhanced FA’s pozzolanic activity. In addition, both the degree of hydration and the compressive strength of the cement paste were considerably improved. The compressive strength reached 67.78 MPa at 7 days, representing an 18.58% increase compared with the control group without GO. The reduced calcium hydroxide content in hydration products indicated that the incorporating of GO in FA-blended cement enhanced the pozzolanic reaction of FA, thereby promoting secondary hydration of the FA.