Dissolution and precipitation behaviours of graphene oxide / tricalcium silicate composites

Abstract

Graphene oxide (GO) modified cementitious materials have the potential to be increasingly applied in a range of important areas due to the enhanced microstructure, mechanical properties and durability. This work presents a thermodynamic-focused analysis of tricalcium silicate (Fe, F–C3S or Alite, simply written as C3S, the main component of ordinary Portland cement) dissolution and calcium silicate hydrate (C–S–H) precipitation rates, which were calculated from the Calcium (Ca) and Silicon (Si) element concentrations in C3S pore solutions, in the presence of GO. The solid phases of GO/C3S composites were characterised by X-ray diffraction (XRD), thermogravimetric analysis (TGA), nitrogen adsorption/desorption analysis and transmission electron microscope (TEM). The element concentrations in the pore solutions of the composites were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Experimental results showed that, within the initial 5 min, the incorporation of 0.03 wt% GO nanosheets resulted in the increase of Si concentration by up to 14.5% while the reduction of Ca concentration by 35.3% in the pore solution, thus, changing the saturation conditions of both C3S and hydration products. After 24 h of hydration, the undersaturation of C3S increased by 2.8% when adding 0.03 wt% GO, and the C3S dissolution rate increased by up to 7.0%. Although the driving force for C–S–H precipitation was inhibited by the incorporation of GO, it was revealed that the overall C–S–H precipitation rate was enhanced throughout the 24 h of hydration. Moreover, GO was found to promote the hydration degree and hydration rate of C3S.