Effect of silica fume and hydroxyethyl methyl cellulose on the properties of cement-sodium silicate grout at high temperatures

The rheological characteristics and mechanical strength of cement-sodium silicate (C-S) grout negatively changed under high temperatures. This study is aimed at investigating the possibility of using silica fume (SF) and hydroxyethyl methyl cellulose (HEMC) to compensate for the decreased properties of C-S grout. The fluidity, gelation time, and rheology for slurry and compressive strength for the hardened state were investigated, and the mineral phase composition and morphology were examined to evaluate the mechanism. Research results indi-cated that the SF and HEMC all decreased the fluidity and extended the gelling time. The addition of SF and HEMC reduced the flowability of the slurries at different temperatures by 5%-50% and 39%-65%, and the setting time was extended by 85.7%-125% and 123.1%-215.4%. Meanwhile, the reduced viscosity in the heat further decreased. For hardened C-S grout, the SF increased the mechanical strength by up to 100% through the physical filling effect, pozzolanic reaction, and mineral phase composition optimization. While HEMC delayed the cement hydration and reduced the strength by 4.6%-57.7%, but had almost no impact on the mineral phase composition and morphology.