Effect of Dilution and Contaminants on Sand Grouted with Colloidal Silica

Colloidal silica is a low-viscosity chemical grout. Samples of grouted sand were made by pouring sand into liquid grout in molds, with the grout diluted to concentrations ranging from 5 to 27% silica by weight. The unconfined compressive strength of the grouted sand, measured after 7 days, was proportional to the silica concentration, up to a maximum of 400 kPa. The hydraulic conductivity of the grouted sand decreased with increasing silica concentration in a nearly log-linear manner down to a minimum of 2 × 10−9 cm/s, and was below 1 × 10−7cm/s for grouts with 7.4% silica or more. Inclusion of 5% volumetric saturation of organics (tetrachloroethene, CCl4, or aniline) in the samples had little effect on the strength or hydraulic conductivity. Samples were immersed in test liquids (organics, HCl diluted to pH 3, distilled water saturated with organics, and distilled water control) for up to 1 year. All samples increased in strength except for those immersed in aniline; samples immersed in water saturated with aniline were also weaker than control samples.