Synthesis of nanoparticles from slag and their enhancement effect on hydration properties of CaO/CaSO4-activated slag binder

Abstract

Developing a low-cost and eco-friendly alternative to cement is of great significance for reducing the CO2 emissions. CaO/CaSO4-activated slag binder may only be served as a promising cementitious material when the severe defect in the early strength is overcame. In this study, gel-like nanoparticles with an average size of ∼ 328 nm were prepared from the slag through dissolution at room temperature and reprecipitation at 50 °C. Subsequently, synthetic nanoparticles (SNPs) were added as a supplementary additive to enhance the strength of CaO/CaSO4-activated slag binder. The effects of SNPs on the strength development, hydration kinetics, hydration products, and microstructure of the slag binders were investigated. The results indicated that the addition of moderate SNPs shortened the duration of induction period and improved the reaction rate in the acceleration period of the slag binders. As a result, large amounts of calcium aluminosilicate hydrate (C-A-S-H) gel was generated at early hydration ages. Meanwhile, SNPs increased the polymerization degree of this gel through the nucleation effect. Gel products’ well-filled the pore spaces between slag particles and yielded a compact microstructure, consequently enhancing the binder strength. The sample with adding 1.5 wt% SNPs exhibited the optimum strengths of 7.78 and 39.86 MPa after 1 and 28 days.