Passive stabilization is a novel ground improvement technique for mitigating liquefaction at developed sites. It is based on the low-gradient (low pressure) injection in the soil pores of colloidal silica, an aqueous dispersion of fine silica particles. This material retains low viscosity values (slightly higher than that of water) up until a well-controlled time, when its viscosity increases rapidly and turns into a gel. When this gel forms in the soil pores, the soil is no longer susceptible to large shear strains and strength degradation related to liquefaction. The (gel) time required for the gelation of colloidal silica is a very important factor for its effective injection at the desired location. It is found to depend on different yet controllable factors such as the pH, ion concentration, ionic strength, percentage per weight of colloidal silica and temperature of the solution. This paper investigates the rheological properties of colloidal silica and quantifies these effects on the gel time as a means for designing this novel ground improvement technique for practical applications.
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