Rheology of cement-sodium silicate grout containing bentonite and cellulose ether at high temperatures

Cement-sodium silicate (C-S) grout is widely used to control water inrush disasters, and its apparent viscosity considerably impacts its water-plugging effect. However, the traditional grouting materials and methods are inappropriate for high-temperature environments, as high temperatures can affect the grout viscosity. Viscosity-modifying admixtures (VMAs) are used to thicken the grout and increase its apparent viscosity. In this study, two types of bentonite (calcium bentonite, Ca-B, and sodium bentonite, Na-B) and hydroxyethyl methyl cellulose (HEMC) were used to modify the C-S grout, and laboratory tests to evaluate fluidity, gelation time, and rheology were performed. The results showed that both bentonite and HEMC decreased fluidity and prolonged gelation time. HEMC, Ca-B, and Na-B decreased fluidity by 46.8–60.4%, 12.5–31.5%, and 17.7–39.1%, respectively, at different temperatures. HEMC, Ca-B, and Na-B increased gelation time by 23.8–50.1%, 23.3–71.4%, and 20%–57.1%, respectively. Additionally, bentonite can partially resist high temperatures and improve the apparent viscosity of grout owing to its water-absorption capacity. Conversely, HEMC has a negative effect on apparent viscosity, which is attributed to the formation of a complex microstructure resulting from intermolecular crosslinking between the cement particles and HEMC, preventing the connection of sodium silicate.