Barriers to achieving highly dispersed graphene oxide in cementitious composites: An experimental and computational study

Graphene oxide (GO) has aroused the interests of researchers as an effective nano-reinforcement for cementitious composites. However, its application to the cementitious environments is severely limited mainly because of its agglomeration. This paper investigates the effect of influential factors including cations, pH value and surfactants on GO agglomeration in the cementitious environments to achieve highly dispersed GO-cement composites. In addition to the experimental studies, molecular dynamics simulations and quantum calculations were also employed to help better understanding of the mechanisms. Results show that multivalent cations like Ca2+ are more detrimental in case of GO agglomeration in the cementitious environment, compared to the monovalents. Moreover, it was found that there is a correlation between the dispersion state of GO and intensity of alkali media of cementitious environment. In mild alkali media, an increment in pH from 7 to about 10.9 causes more ionization and electrostatic repulsion, which leads to better dispersion. However, at high alkali media with pH larger than 10.9 GO dispersion undergoes reduction when pH increases. It is because GO loses the majority of its functional groups and eventually agglomerates. Among examined surfactants, polycarboxylate ether based super plasticizer shows the best capability to disperse GO in the cementitious environment. (C) 2018 Elsevier Ltd. All rights reserved.