Abstract:

Silica sol has great application prospects in the field of anti-seepage grouting due to its good permeability and injectivity，strong durability，non-toxic and environmental protection.The practical application of single silica sol is limited due to its poor solidification controllability.Adding salt solution/acidity regulator and both can regulate the solidification behavior of silica sol.However，the influences of salt solution and acidity regulator on the composition，viscosity and setting time of silica sol and their mechanisms are still not completely clear.In this paper，calcium chloride solution and acetic acid were selected and added to silica sol respectively or simultaneously to study their effects on the composition，viscosity and setting time of silica sol and elucidate their effects mechanism.At the same time，the strength and permeability coefficient of silica sol/calcium chloride/acetic acid system were investigated.The results showed that calcium chloride could significantly promote the condensation of silica sol，and the viscosity of silica sol was increased rapidly in a short time.After the addition of acetic acid，the viscosity of silica sol was increased slowly and the setting time was longer.When calcium chloride and acetic acid were added at the same time，the viscosity of silica sol experienced a slow increase at first，and then a rapid rise，and the setting time of silica sol could be effectively controlled by controlling the concentration of calcium chloride.After the addition of silica sol/calcium chloride/acetic acid system，the 3 d compressive strength of silica sol solid sand body was greater than 0.39 MPa，and the permeability coefficient of silica sol solid sand body could be maintained in the range of 1×10^-9 cm/s.The results could provide a theoretical basis for the preparation of silica sol grouting materials and their application in the field of grouting.

Key words: silica sol, grouting material, viscosity, setting time, permeability coefficient