Polished concrete is a concrete surface that has been mechanically refined to exhibit a reflective shine similar to granite or marble tiles. The shine, when done properly, is a natural finish that will not peel or flake like a conventional wax or coating.
The process by which polishing takes place relies upon the concrete surface being smooth and free from any pits, due to age or aggregate exposure, that would otherwise limit the ability of the shine to be clear.
Think of a mirror’s reflection and the reflection in a car’s polished paint. The degree of the clear reflection is termed as clarity. Clarity will be better or worse depending on the polished surface’s soundness. If there are voids, called pinholes, then those voids will not reflect light or an image. This will result in a loss of reflection clarity.
Grout application makes a huge difference in reflection of light
Grout, in its purest meaning, is any suitable material that fills the pinholes and polishes similarly as the concrete that surrounds it. For the suitability of any grout material, it should be any material that will have a durability similar to the concrete so that it wears like the concrete and reflects light as the concrete does so its use is as camouflaged as possible to eliminate any noticeable color or shine variation. Epoxy or cement based grouts are most common but there are other specialty products.
Epoxy grout is the simplest to use since quality resin and related products essential to the process can be sourced from multiple sources. Epoxy has a viscosity that is ideal to fill the pinholes, hardens to a workable state in eight hours, is harder than most concrete, and will polish similar to the concrete it fills.
The installation of the epoxy to complete the grout process varies but it’s installation is relatively simple. Being that the epoxy has a flowing consistency, it’s simple to trowel the epoxy across the surface of the concrete in a manner that it flows into the pinholes and fills them a little more than flush of the concrete surface.
Once the epoxy is installed, and after the subsequent hardening period, the floor is then ground as it normally would be to continue the polishing process. As the floor is polished the epoxy grout becomes polished the same way and at the same rate as the concrete. The final result is a floor that is free of pinholes and has a natural looking appearance as though the only material used was concrete.