Hydration of blended cement with high-volume slag and nano-silica

Abstract

Utilization of nano-silica is an effective method to improve the early properties of blended cement containing high-volume slag. In current work, the hydration of blended cement with high-volume slag (40 wt%, 60 wt% and 80 wt%) and nano-silica has been investigated by testing setting time, heat of hydration, compressive strength, hydration products and pore structure. The results illustrate that nano-silica can improve the hydration of slag and cement (including tricalcium silicate (C3S) hydration and transition from ettringite to monosulfate) before 3 d. The increased slag content affects the promotion of nano-silica on cement hydration. Besides, nano-silica inhibits the hydration of cement after 3 d. Furthermore, nano-silica can improve the content of chemically bound water and reduce Ca(OH)2 content. Combined use of appropriate content slag and nano-silica can better optimize the pore structure of hardened pastes, including pore size and cumulative porosity. Ultimately, nano-silica enhances the compressive strength of hardened paste, but the improvement effect of nano-silica gradually weakens with the increase of slag content and the extension of curing time. This paper can provide a theoretical basis for nano-silica modified cement with high-volume slag, and help to improve the early performance of cement with high-volume slag.