Influence of salinity on the gelation and microstructure of cement–sodium silicate grout

This study investigates the influence of salinity on the gelation behavior and microstructural characteristics of cement–sodium silicate (CS) grout, aiming to optimize its performance for ground reinforcement in saline environments. A robust multi-scale experimental program was conducted, combining microstructural analysis with laboratory and pilot field tests. Laboratory tests examined the effects of varying water-to-cement (W/C) weight ratios, cement-to-sodium silicate (C/S) volume ratios, and salinity conditions (0.01%, 1.38%, and 2.87%), along with Uniaxial Compressive Strength (UCS) measurements. Microstructural evaluation included density, heterogeneity, particle size distribution using X-ray computed tomography (CT) and field emission scanning electron microscopy (FE-SEM), with heterogeneity quantified through Madogram analysis. Pilot-scale tests were conducted under 0% and 3% salinity conditions. Results showed that higher salinity accelerated gelation, reducing fluidity and complicating grout injection. CT and FE-SEM analysis revealed increased density, larger pores and more pronounced calcium hydroxide formations under saline conditions. Madogram and particle size data indicated greater heterogeneity and larger voids, suggesting reduced mechanical strength and durability. Pilot tests confirmed these findings, highlighting practical challenges in saline environments. Overall, the study emphasizes the need for tailored grout formulations and adaptive injection strategies. It offers a valuable framework for understanding CS grout behavior under varying salinity, supporting improved design in civil engineering applications.