A LOOK DEEPER INTO POLISHED CONCRETE FLOORING
When choosing to polish concrete there are many options to make sure the floor looks and performs to your standards. Some of these options include deciding on the final polishing grit or shine of the floor, or choosing what color will look just right in the space. One of the features that I have seen overlooked in these design decisions is the aggregate exposure of the finished floor, or how deep the grinding phase of the concrete will go into the concrete. This decision can have a big impact on the final look of the space as extensive grinding can remove the surface layer of the floor exposing the inner workings of the concrete.
Choosing the depth of the polish determines the aggregate exposure of the final finished floor. The choice to expose the aggregate in polishing in purely a cosmetic choice, but aggregates role in the structural concrete is key for strength. Here’s a quick rundown of aggregate and its role in concrete – In its basic state concrete is made up of cement powder, small aggregate, large aggregate and water. The aggregate is typically a locally mined sand and rock. The concrete gets strength by the cement powder and water acting as a glue that holds all of this very hard and strong stone and sand in a fixed place.
In a typical concrete floor you would never see the aggregate. The finishing process involved with new concrete flooring pushes the aggregate into the concrete mix allowing the cement paste and water (cream) to rise to the surface so finishing can proceed and produce a nice smooth floor. When choosing to grind deep into the concrete we remove this cream layer resulting in exposing the aggregate (stone and sand) in the concrete. Let’s take a look at the 3 different exposure levels.
Option 1 – Cream Finish
This finish level polishes the top layer of the concrete. This is the most affordable option and also provides the most color movement and shifting when using concrete dyes or stains to color the concrete. This will show some of the tooling marks from the finishing process of pouring the concrete. This finished floor has a lot of movement and shifting in the surface.
Option 2 – Light Exposure
This finish level exposes the sand and small parts of the larger aggregate. When using aggressive diamond abrasives to remove a glue or sealer from the concrete this is typically the finish unless deeper grinding is wanted. When staining this type of floor a more monochromatic color will be achieved.
Option 3 – Heavy Exposure
This finish level fully exposes the larger aggregate in the concrete. This gives the concrete a terrazzo type look. This finish is typically the most expensive as it involves extensive grinding at the beginning part of the concrete polishing project. When grinding this deep, a grouting process; used to fill air voids in the concrete, is also recommended.
One of the most unique aspects of concrete flooring is that every floor will have its own unique look. This is very true when exposing the aggregate in the concrete. Different regions all have rocks that are natural to the area. For example concrete made in Utah may contain granite as the main aggregate, while concrete made in Florida may contain softer aggregate such as seashells. When pouring a new concrete floor or using a self-leveling overlay material, decorative aggregate such as marble chips, or glass chips can also be broadcast into the wet concrete mix so these are exposed during the polishing process for a customized look.