A Feasibility Study of Colloidal Silica as Stabilizing Material for Passive Site Remediation

Passive site stabilization is a ground improvement method that causes minimal disruption to the site being treated. The concept is to allow a low-viscosity fluid to flow to the target area that solidifies there and create a bond between soil particles. Colloidal silica can be used as a stabilizing material in passive site remediation. This paper explores the chemical processes that are required to initiate the gelling process in colloidal silica. pH and ionic strength are the two parameters that most affect the gelation of colloidal silica. The paper aims to explore optimum pH and corresponding salt content which provide workable gel time in the field. Gel time has been observed for a maximum of 120 days at different pHs and, gel time curves are plotted for various combinations. It was found that increasing salt content leads to a decrease in the gel time. A pH range of 4.5–6.2 has been observed as the most optimum pH range. To find out the effects of gelation in the sand, unconfined compression tests were performed. Samples of 40% relative density grouted with four different colloidal silica percentages under a curing period of 3, 7 and 28 days were tested. A total of 36 samples was tested. It was found out that the strength of the treated sand increases with an increase in colloidal silica percentage and curing time. As a result of the findings of the present research, colloidal silica can be proposed as a suitable stabilizer for non-disruptive liquefaction mitigation.