Incorporation of graphene oxide and silica fume into cement paste: A study of dispersion and compressive strength

• Dispersions of graphene oxide in pore solution and cement paste was studied.
• Mechanism of GO aggregation in cement paste is cross-linking of calcium cations.
• Silica fume is effective to improve GO dispersion in cement paste.
• Appropriate amount of silica fume improves GO dispersion and compressive strength.

As a 2D nanomaterial, graphene oxide (GO) has attracted considerable attentions for reinforcing cementitious materials. However, special attention must be paid to the dispersion of GO in the matrix, as the quality of nanomaterial dispersion correlates directly with its effectiveness for improving mechanical and other properties. In this study, the dispersion of graphene oxide (GO) in simulated pore solution and cement paste was investigated. It was found that severe GO aggregation occurred in presence of divalent calcium ions in both pore solution and cement paste. However, the GO aggregates were not stable under shear mixing. After vigorous mixing, the massive GO aggregates split into medium-sized particles, ranging from few to several 100 μm. To improve the GO dispersion in cement paste, silica fume was used to mechanically separate individual GO nanosheets. The dispersion was then investigated using microstructure analysis and mechanical properties. The results showed that, with the addition of silica fume, the dispersion of GO nanosheets was greatly improved.