Mechanical properties, microstructure and consolidation of sand modified with sodium silicate

Grouting is an effective way to address the poor performance of sandy soils. There are few studies on water glass single-liquid permeation grouting for solidifying sandy soils. To study the effects and processes of water-glass-cured sandy soil, we conducted a direct shear test and uniaxial compressive strength test on water-glass-cemented sandy soil specimens and summarized the relationships among modulus, Baume degree, curing time and strength of cured sandy soil from a macroscopic mechanical point of view. By combining nuclear magnetic resonance (NMR) imagery and scanning electron microscopy (SEM), the consolidation evolution of cured sandy soil was revealed from a microscopic point of view, including the pore structure and gel state. The results showed that there is a saturation value for the strength of water-glass-cured sandy soil. The specimens with a low Baume degree solidified quickly, the strength saturation value was lower than 3 MPa, and the inner layer was dehy-drated in a loose sand state; the specimens with a high Baume degree solidified slowly, and the strength satu-ration value was higher than 8 MPa. The migration of water glass and the deepening of curing are the two processes that control the effect of consolidation. The state of the silica gel plays a decisive role in the strength, the saturation value of the specimen strength depends on the limit of gel condensation, and the thickness of the gel layer is exponentially related to the strength. In addition, high-modulus and high-Baume degree water glass is recommended for consolidation when an improvement in the strength and compactness of sandy soils is needed.

Automated summary

This study investigated the effects and processes of water-glass-cured sandy soil by conducting direct shear tests and uniaxial compressive strength tests. The relationships between modulus, Baume degree, curing time, and strength of cured sandy soil were summarized from a macroscopic mechanical point of view. The consolidation evolution of cured sandy soil, including pore structure and gel state, was revealed from a microscopic point of view using nuclear magnetic resonance (NMR) imagery and scanning electron microscopy (SEM). The results showed that the migration of water glass and the deepening of curing are key processes controlling the consolidation effect. The state of the silica gel plays a decisive role in the strength of the cured sandy soil.