Hydration and synergistic features of nanosilica-blended high alkaline white cement pastes composites

Abstract

AbstractNanosilica (NS) behavior on hydration and synergistic characteristics of highly alkaline (HA) white cement pastes composites containing 5–25 mass % of NS (as substitution) was studied. The hydration kinetics behavior from 1 to 100 days was examined for all the blends e.g.: whiteness reflection (Ry), setting, compressive mechanical strength (CS), bulk density (BD), combined water content (Wn), total porosity (TP), and free lime (FL) have all been checked. The substitution of 5 wt.% NS has improved the compression mechanical strength and physico-chemical features of HA-white cement pastes composite, especially the compressive mechanical strength, free lime content and bulk density. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques have been implemented to investigate the microstructure and features of NS pastes composites. NS (5%) improved the synergistic and hydration properties of the evaluated composite materials. NS has a substantial impact on the performance of HA-white cement composite pastes, reducing whiteness reflection (Ry), total porosity and setting times while enhancing mechanical strength, bulk density and gel-to-space ratio. SEM showed a thicker fiber microstructure and more calcium silicate hydrate products lead to a sharp decrease in porosity of all NS composites so it enhances the mechanical and physical properties, as well as the original morphology of calcium mono-carboaluminate hydrate. Highly recommended NS cement composite containing 95 percent + 5 percent NS has better performance and synergy than ordinary white cement. It showed a compact, high-density microstructure consisting of a large proportion of the microcrystalline fibrous group leading to reduced porosity of the blend.