Colloidal silica and polished concrete

Factory background with concrete floor, night scene.

By Sheldon White

Colloidal silica post-placement pozzolan technology can benefit polished concrete in many ways.

Polishing entails removing the upper paste portion of the concrete surface to achieve a specific aesthetic finish. Depending on the desired appearance, polishing exposes fine and/or coarse aggregates in the concrete. During the process, a densifying liquid is used to harden the concrete by filling capillaries and pores at the surface.

Colloidal silica benefits

At time of placement, colloidal silica post-placement pozzolan technology reduces drying shrinkage of the concrete slab. Colloidal silica post-placement pozzolan technology also densifies concrete within the interaction zone. Moreover, it provides a superior cure, while also increasing the durability of concrete and, therefore, maintenance requirements. Notably, colloidal silica post-placement technology allows floors to be polished within 14 days of concrete placement. This is a significant benefit that our colloidal silica post-placement pozzolan technology brings to all flooring projects.

Colloidal silica post-placement pozzolan

Colloidal silica post-placement pozzolan technology penetrates concrete through the concrete capillary system. Colloidal silica post-placement pozzolan technology then reacts with free alkali within the concrete. The reaction creates Calcium Silicate Hydrate (C-S-H) that essentially fills the pores and capillaries with more concrete and, in doing so, densifies the slab.

Colloidal silica and polishing

Polished concrete that has been treated with colloidal silica post-placement pozzolan technology may have a lighter appearance. Moreover, concrete treated with colloidal silica post placement pozzolan technology may be harder to grind. Typically, the timeframe for grinding concrete treated with colloidal silica post-placement pozzolan technology is similar to that of high-performance concrete. Many colloidal silica post-placement pozzolan-treated slabs have been ground and polished without the use of an additional densifier with excellent results. Nevertheless, contractors can still use a densifier on slabs treated with colloidal silica post-placement pozzolan technology if it has been specified for their project. Using a densifier will not deter the performance of colloidal silica post-placement pozzolan technology in any way. However, Spraylock Africa recommends always performing a test on a sample before polishing an entire area that has been treated with colloidal silica post-placement pozzolan technology. A topical sealer may also be used to help reduce staining of concrete.