Hydration of C3A/gypsum composites in the presence of graphene oxide

Abstract

The interactions between graphene oxide (GO) and individual clinker phases, which are critical for understanding the mechanism of GO during the hydration of cementitious materials, remain unclear. Therefore, this study investigated the effect of GO on the thermodynamic-based solution chemistry and hydration of tricalcium aluminate (C3A), which is a main constituent phase of Portland cement, in the presence of gypsum. The pore solution composition, phase content, and morphology of C3A/GO/gypsum composites were studied by inductively coupled plasma optical emission spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The experimental results showed that the incorporation of GO led to Ca2+ adsorption, which particularly decreased the local Ca2+ concentration near the surface of C3A. This increased the undersaturation levels of C3A and gypsum, thus facilitating their dissolution. A lower Ca2+ concentration led to a slight decrease in the supersaturation of hydrates after GO addition. Nevertheless, the introduction of GO improved the overall hydration degree, as confirmed by quantitative X-ray diffraction and thermogravimetric analysis. This improvement can be probably attributed to the higher number of nucleation sites provided by GO for precipitation. In addition, the scanning electron microscopy images of C3A/gypsum paste showed a cluster-like structure composed of coarse needle-like ettringites.