The effect of graphene oxide-fly ash hybridisation on the hydration, microstructure and mechanical characteristics of cement concrete

Abstract

Carbon-based nanomaterial graphene oxide (GO) can improve cement composites strength and toughness but reduce fluidity. Fly ash is the most common cement substitute for improved fluidity and durability, but early strength growth may be slower. The effects of GO and fly ash on concrete hydration, morphology and mechanical characteristics should be further investigated. GO addition to concrete at 0.025% and 0.05% was investigated by partially replacing cement with fly ash at 10% and 20% by weight. GO addition reduced the concrete fluidity, but the substitution of fly ash increased the fluidity. Moreover, GO compensated for the delayed strength growth of fly ash-based concrete at early-age. The strength properties of GO and fly ash-based concrete at 7 and 28 days are greater than control concrete. Hydration, morphology and elemental composition of concrete were characterised using TGDTA, SEM and EDX. The results demonstrated that GO accelerated cement hydration at early age. Furthermore, GO influenced the total hydration of concrete by expediting secondary hydration of fly ash at later age. Similarly, the morphology of concrete matrix was improved by interweaving hydrated products. This study suggests that using GO and fly ash to produce concrete is an effective process for achieving high performance.