Durability of cement-sodium silicate grouts with a high water to binder ratio in marine environments

Abstract

This study aims to investigate the durability and microstructure of cement-sodium silicate grouts with high water to binder ratios (w/b) of 1.1–2.5 upon exposure to sea water. Grout specimens were prepared by mixing ordinary Portland cement paste and 4.4–7.5 wt% sodium silicate (water glass solution), which was adopted as an accelerator to prevent dilution and displacement during injection for geological strengthening and water control. The setting time, sulphate attack resistance, permeability and autogenous shrinkage of the grouts were assessed and compared. The microstructures were investigated in terms of the morphology and structure of the pores and cracks.The results reveal that satisfactory properties and durability, such as a setting time of 60–120 s, a flexural strength reduction of −3–6% after sulphate attack by sea water, a permeability of 1.2–1.6 MPa and an autogenous shrinkage of −0.298–1.22 milli, were obtained in cement-sodium silicate grouts with a w/b of 1.1–1.6 and dosages of sodium silicate of 4.4–5.7 wt%. However, hardened grouts suffered serious deterioration due to sulphate attack in 3 wt% sodium sulphate solutions and fatal drying shrinkage when exposed to air with a relative humidity of 60% at 20 °C. The cement-sodium silicate grout with the recommended composition is feasible and durable in marine environments, but special care must be taken when this grout is applied in environments with a high sulphate concentration or wetting-drying cycles.