Bentonite hydration effects on the engineering properties of a cement - sodium silicate slurry

Because of the advantages of good fluidity, short gelation time and high compressive strength, cement - sodium silicate slurry is widely used in shield engineering. Bentonite is an important component of cement - sodium silicate slurry in shield engineering. Currently, it is important to clarify the bentonite hydration to enhance the engineering properties of the cement - sodium silicate slurry. Therefore, to understand the bentonite hydration process, the electrical conductivity of bentonite slurry tests were conducted at different bentonite hydration times. The electrical conductivity was considered to be inversely proportional to the free water in bentonite slurry. And the electrical conductivity increased and then decreased with increasing bentonite hydration time. The bentonite - cement slurry bleeding rate, fluidity, the two - component slurry gelation time and compressive strength tests were investigated at different bentonite hydration time, and these parameters decreased and then increased with increasing bentonite hydration time. As for the bentonite A, the ranges of the electrical conductivity, bleeding rate, fluidity, elation time and 28d cured strength range were 610-742 μs/cm, 6.40-7.15%, 34.5-43 cm, 48-70 s and 23.2-28 MPa, respectively. Under different bentonite hydration time conditions, XRD and SEM tests were carried out to analyse the effect of bentonite hydration time on the compressive strength of the cement - sodium silicate slurry 28 days cured samples. This is mainly due to the fact that the calcium silicate hydrate (C-S-H) content decreased and then increased with decreasing the bentonite hydration time. The research results can provide data support for the design and construction of the cement - sodium silicate slurry in shield engineering.