Dispersion of graphene oxide–silica nanohybrids in alkaline environment for improving ordinary Portland cement composites

Abstract

2D nanomaterials such as graphene oxide (GO) nanosheets have demonstrated marked potential for reinforcing and functionalizing ordinary Portland cement (OPC) composites. Yet despite its excellent intrinsic properties, the poor dispersion of GO in cement matrix hampers its effectiveness in enhancing the performance of OPC composites. In this study, GO was modified by tetraethylorthosilicate (TEOS) to synthesize thin hybrid GO-SiO2 nanohybrids (GOS). The GOS was characterized and its dispersion behaviour in cement pore solution was compared to that of GO. The results demonstrated that GOS had significantly longer dispersion stability than GO. We propose that the formation of a thin silica coating on GOS prevented cross-linking between Ca2+ ions from solution and carboxylate groups from GO. The thin silica coating also functioned as a spacer and minimized agglomeration caused by van der Waals forces. The effects of GOS on the workability and mechanical properties of cement mix were also investigated. Compared to batches with GO, GOS nanohybrids provided additional 26% and 22% enhancements of compressive strength and 21% and 31% enhancements of tensile strength at 7 and 28 days respectively. These results demonstrate the strong potential of our novel method for improving GO dispersion in a cement environment and for increasing the strength of OPC composites reinforced by nanomaterials.