By Jamie Krueger
Floors in industrial or commercial settings, such as department stores and warehouses, are under a lot of strain from constant traffic. When looking for a flooring option, functionality is a primary concern. In addition to epoxy, vinyl composition tile (VCT) or terrazzo, polished concrete is gaining traction as an option due to its strength, abrasion resistance and low maintenance; it is also aesthetically pleasing. Since polished concrete is relatively new compared to other flooring types, it is important to understand why it is a good option for industrial/commercial floors.
Polished Concrete vs. Other Finishes
There are several applications on the market that can make a floor look like it was polished, but it really has a coating. It is important to know the differences between a polished concrete surface and coating treatments to ensure the end result is what architects and building owners intended.
Polished concrete has a wide array of finishes and variables to consider. These include different aggregate exposure levels, gloss levels and even whether or not to dye the surface with one or several colors. With that said, most industrial and commercial floors tend to have a low to medium gloss finish with semi-exposed or low-exposed aggregate floors. A salt and pepper finish is very common. This level of exposed aggregate opens up the concrete enough for a densifier to soak in and react with the concrete. Exposing larger aggregate costs would raise costs significantly. Also the gloss level tends to be lower than a highly decorative finish not only due to the price, but also the slip resistance is greater when not highly polished.
Where once epoxies and VCT were the norm, building owners are seeing the benefits of polished concrete. With polished concrete, floors do not have to be re-epoxied every few years due to the epoxy failing from fork truck traffic, water issues, oil entrained floors, poor surface preparation, etc. Over the long term, polished concrete is a much more cost efficient floor; not only because of longevity, but also due to less downtime from having to move equipment to re-epoxy every few years. Polished concrete is a long term flooring solution with the right maintenance program. Using concrete is also a “greener” building material because there are no additional materials needed.
Commercial/industrial floors typically need to be flat and in some cases, floors have specific specifications. Since polished concrete starts with grinding, a flat floor can be achieved. Most of the time flattening a warehouse floor is required when there is heavy fork lift traffic. Uneven floors can be caused by control joints heaving due to the floor moving and therefore a lippage is created. This lippage can be very dangerous because every time a fork lift runs over it, the bump could cause the load to fall off the lift. To solve this problem, the use of an aggressive grit metal tool effectively cuts off the lip. However, a different aesthetic look will result where the previously high-side of the heave will have exposed aggregate and the low-side will have the same overall look, unless the entire floor is cut down to an exposed aggregate level.
Industrial/Commercial Finish Polishing Steps
When creating a floor for an industrial/commercial facility, there are several steps to follow to ensure the installation will be done properly.
Grinding for Flatness
Normally, industrial or commercial floors do not need a fully-exposed aggregate look, so starting with a very aggressive grit is not necessary. However, there are few instances in which using an aggressive grit, like a 20 grit metal diamond, is necessary. These instances include removing an existing covering or flattening a floor. To achieve a flat floor, a full set of diamonds should be used instead of a half set. The full set will tend to keep the head more rigid, whereas the half set acts like a tripod and results in a wavier floor.
- Use a metal-bond diamond tool, either a 20 or 30 grit, to level out large differences in the surface or to remove any coatings on an older floor. If a floor does not have a lippage issue or coating, starting with a 50 or 60 grit metal diamond or a 100 or 120 grit metal diamond is the first step. The first cut will obtain the look the building owner wants. The first cut is also used to open up the floor enough for the densifier to be absorbed. If the floor is not opened up enough, the floor will not be as hardwearing as it could be and the life of the floor will decrease. If starting with a 50 or 60 grit metal diamond, use the 100 or 120 grit metal diamonds next to ensure the 50/60 scratch marks are reduced.
- It is usually a good idea to use a grout to fill in the air pockets, pin-holes and hair line cracks created when grinding. Grouts result in a much cleaner floor with better clarity. Acrylic-based grouts are very easy to use and are applied during the last stage of metal-bond diamond grinding. To apply, spray a little water to dampen the floor and then pour the grout on and “broom in” (the broom will clean out the dust in the pores). While the acrylic-based grout is still wet, grind over the surface with a grinder using 100 or 120 grit metal diamonds. This creates a slurry and fills the pores. Next, use a foam squeegee to clean the floor, do not use a broom or vacuum as this may remove some of the grout in the pores.
- It is a good idea to densify the floor at this point. The densifier will harden the cement and grout, so the grout will not fall out when grinding. Hybrid diamonds, such as ceramics, can be used after the densifier has completely dried. These hybrid diamonds are more aggressive than resins and help beginner operators remove random scratching that may have been left by the metal-bond diamonds. 100 grit hybrids should be followed by 200 grit hybrids. These grits are honing the concrete and should eliminate all visible scratches.
- Next, polish with 400 grit resin. This might be the last step depending on gloss specifications. If needed, 800 grit resin pads can be used to achieve further gloss and clarity on the floor. The 400 grit resin closes the floor enough to be a polished surface and still have a good slip coefficient.
- The final step is applying a guard to the finished floor. A guard is usually a better option for a high traffic area than a topical sealer. The major difference is that a guard penetrates into the concrete and only leaves a residue on the surface. When the concrete is fully cured, the guard is buffed off and the concrete is then a wear surface. A sealer is topical and usually needs to be heated with a high speed burnisher to cure. While both will protect the floor, the sealer will eventually wear away and need maintenance in high-traffic areas.
Department stores and warehouses are always looking for new, cost-efficient and “greener” ways to enhance their facility. Knowing the basics of industrial/commercial polishing can give these facilities another flooring option with endless possibilities.