Study on the performance of magnesium oxide enhanced cement-based grouting materials in composite chloride environments

This study presents a high-performance MgO-cement-based grouting material designed to address poor solidification in saline groundwater environments. The effects of varying salt content (0%- 25 %), liquid-solid ratios (0.5, 1.0, 1.5), and MgO content (5%-25 %) on grouting performance were investigated. Tests examined slurry workability and mechanical properties of the cemented body, while XRD and SEM analyses explored hydration mechanisms. Results indicate that salt content, liquid-solid ratio, and MgO content significantly influence performance. As salt content increases, slurry water separation and fluidity decrease, while viscosity rises. Low salt content can enhance the rate of cement hydration and shorten the setting time. Microscopic analysis reveals that a 5 % salt content results in the most compact and uniform microstructure, suggesting that an appropriate amount of chloride salts can improve the pore structure. Increasing the liquid-solid ratio leads to higher water separation rate and fluidity of the slurry, and lower viscosity. A higher liquid-solid ratio dilutes the slurry concentration, increases the distance between cement particles, and prolongs the setting time. When the salt content is 20 % and the liquid-solid ratio is 1.0, adding MgO increases the water separation rate, decreases fluidity, and increases viscosity of the composite chloride salts cement slurry. The setting time of the slurry rapidly decreases with 5 % MgO and then increases linearly. At 5 % MgO, the microstructure of the cemented body is wellstacked, dense, and orderly layered, significantly improving the compressive strength of the material.