Edge-oxidized graphene oxide (EOGO) in cement composites: Cement hydration and microstructure

In this study, the effects of edge-oxidized graphene oxide (EOGO), which is a relatively low-cost carbon-based nanomaterial, in a cement composite were investigated with microstructural and crystallography analyses. EOGO was produced from graphite through a mechanochemical process characterized by advanced material conversion methods. The positive effect of EOGO on the strength improvement of cement composites was found in previous studies, however, a reaction mechanism between EOGO and cement hydration products was not clearly identified. The current paper utilizes these strength results to investigate the mechanism of the strength improvement of EOGO-cement composite. Comprehensive research studies, X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) analysis and heat of hydration analysis, were conducted to investigate the mechanism of EOGO in strength, microstructures and crystalline phase change of cement composites over time. The design variables explored in the mixture include EOGO content (ranging from 0.01% to 1%), use of a water-reducing admixture (superplasticizer) and mixing method. The mix design method is classified into two designs: (1) dry-mix design of EOGO mixed with cement as a dry powder prior to paste formation and (2) wet-mix design of a sonicated EOGO solution used during paste formation. It was found that 0.05% of EOGO is the optimum content to achieve the highest strength for most EOGO-cement composites. In addition, the dry-mix design, which is more practical and feasible was competitive over the wet-mix design. The crystalline phase change results show that EOGO plays a positive role for Nano-seeding the material into the cement mixtures.