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

Cement–sodium silicate grout (CSG) is widely used to control water inrush disasters, and its apparent viscosity considerably impacts its water-plugging effect. However, traditional grouting materials and methods are inappropriate for high-temperature environments as high temperatures can affect the grout's viscosity. To thicken grout and increase its apparent viscosity, viscosity-modifying admixtures can be used. In this work, two types of bentonite (calcium bentonite (Ca-B) and sodium bentonite (Na-B)) and hydroxyethyl methyl cellulose (HEMC) were used to modify CSG and laboratory tests were performed to evaluate the fluidity, gelation time and rheology. The results showed that both bentonites and the HEMC decreased fluidity and prolonged the gelation time. HEMC, Ca-B and Na-B decreased the 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 the gelation time by 23.8–50.1%, 23.3–71.4% and 20%–57.1%, respectively. 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 cross-linking between the cement particles and HEMC, preventing the connection of sodium silicate.