Dissolution and precipitation behaviours of graphene oxide / tricalcium silicate composites. (1st April 2020)

• Record Type: Journal Article
• Authors: Kang, Xiaojuan; Zhu, Xiaohong; Liu, Jiaping; Shu, Xin; Huang, Yongbo; Qian, Jueshi
• Is Part Of: Composites. Number 186(2020)
• Publication Date: 2020-04-01
• Subjects: Graphene oxide (GO) -- Dissolution rate -- Precipitation rate -- Tricalcium silicate (C3S); Composite materials -- Periodicals; Materials science -- Periodicals; Composite materials; Periodicals; Electronic journals; 620.118
• DOI: 10.1016/j.compositesb.2020.107800
• Languages: English
• ISSNs: 1359-8368

Abstract

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–C3 S or Alite, simply written as C3 S, 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 C3 S pore solutions, in the presence of GO. The solid phases of GO/C3 S 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 C3 S and hydration products. After 24 h of hydration, the undersaturation of C3 S increased by 2.8% when adding 0.03 wt% GO, and the C3 S 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 C3 S. Highlights: GO can increase the Si concentration while reducing the Ca concentration during the first 2 h of hydration. GO can improve the undersaturation of C3 S and supersaturation of portlandite while reducing the supersaturation of C–S–H. GO can facilitate both dissolution rate of C3 S and precipitation rate of C–S–H. GO can promote the overall hydration degree and hydration rate of C3 S.