Colloidal silicas also know as nano-silica / Nano-sols are used as an accelerator in cement  systems as they reduce thickening time of cement. Colloidal silica increases the compressive strength, helps with gas migration control at high temperatures, and decreases fluid loss by decreasing the permeability of set cement. COLLOIDAL-SIL™  and GEO-SIL™ for geo-polymer cementing applications are available  in a variety of grades depending on use and application.