Experimental and molecular dynamics studies on the durability of sustainable cement-based composites: Reinforced by graphene

Due to the well impervious of graphene-based materials, it has been considered as a potential additive to enhance the durability of a sustainable cement-based material. In this paper, graphene oxide (GO), as a unique 2D nano-reinforcement, has been introduced in the cement materials. The systematical investigation of the transport properties of GO-cement composites was performed by using the chloride diffusion tests, microstructure characterization and molecular dynamics study. A very low fraction of GO (0.011 wt %) can significantly reduce the diffusion of chloride and the average chloride depth was dropped by 28.6% compared to the plain samples. The improved barrier properties can be attributed to the refined microstructure induced by GO, such as the reduced porosity of macropores and the prohibited cracks. Furthermore, the molecular dynamics modeling help understand the "immobilizing" and "caging" mechanism of GO incorporation. The oxygen-containing functional groups of GO give enough oxygen sites to accept proton and bind to adjacent sodium ions, which fix H2O and ions on surface. In particular, the surficial Ca2+ on surface plays a bridge role between the oxygen on surface and the functional groups, which enhances the interfacial chemical bonds. The results indicate that the incorporation of GO in cement composites can be practically used to enhance the durability of cement-based structures. (C) 2020 Published by Elsevier Ltd.