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 dilut ed to concentrations ranging from 5 to 27% silica by weight. The unconfined compressive strength of the grouted sand, measured after 7 days, was propo rtional to the silica concentration, up to a maximum of 400 kPa. The hydrau lic conductivity of the grouted sand decreased with increasing silica conce ntration in a nearly log-linear manner down to a minimum of 2 x 10(-9) cm/s , and was below 1 x 10(-7) cm/s for grouts with 7.4% silica or more, inclus ion of 5% volumetric saturation of organics (tetrachloroethene, CCl4, or an iline) in the samples had little effect on the strength or hydraulic conduc tivity. Samples were immersed in test liquids (organics, HCl diluted re pH 3, distilled water saturated with organics, and distilled water control) fo r up to 1 year. All samples increased in strength except for those immersed in aniline; samples immersed in water saturated with aniline were also wea ker than control samples.