As polished concrete increases in popularity, many people discover that it is harder to keep up than they thought. The concrete floor was once common only in garages. Still, over the last decade, industrial buildings in large cities have been turned into lofts and condominiums. Their concrete floors are polished to a marble-like luster garnering much attention from design magazines and home improvement enthusiasts.
Today, the polished concrete slab is used not only as flooring but also as a cheap alternative to stone countertops. However, suppose you want a polished look and want to avoid the high cost of hiring a professional polisher. In that case, you will need to learn how to polish concrete floor yourself. Other places where you may need to polish concrete are patios, lanais, driveways, walkways, and pool decks.
Is Your Concrete Ready to Polish?
Almost all concrete slabs can be polished. Suppose you are laying your own concrete floor or countertop. In that case, however, it must be completely dry before you start the polishing process. In most cases, wet concrete will have to sit for three days before it is dry enough to polish. To test it for dryness, use a power sander on a small, out-of-the-way segment. If the sander kicks up large pieces of sand, wait another twenty-four hours before trying again.
Some concrete slab has been painted, lacquered, or otherwise finished. Your concrete must be completely free from finishes or inlays before you start polishing. Although the polishing process will remove the finish as you go, it can be difficult to see how deep you are going if you are not starting out with a clean slate. Any inlays in your concrete slab can result in an uneven finish with rough, unpolished patches.
Once your concrete floor is dry and all finishes have been removed, it must be thoroughly cleaned, patched, and sealed. You should use an industrial strength solution made of butyl cleaner and degreaser to clean the floor. Make sure that the cleaner has dried completely before you start patching any holes, chips, or cracks.
Regarding patching, the best material for the job is a concrete adhesive patch. Using a chisel, you can cut out and shape any existing holes so that they are larger on the bottom than on the top of the concrete slab. Mix the adhesive according to the instructions on the package, and apply the patching compound to each hole, using a trowel to smooth it out even with the surface of the floor.
If you are refinishing a floor, use a layer of self-leveling concrete instead of individual patching. Self-leveling concrete quickly allows you to refinish a concrete floor that has become uneven or pitted from traffic, weather, or subfloor movements.
After patching, it is recommended to apply a concrete sealer. This will protect the bare concrete against wear and corrosion. There are several types of concrete sealer, but the two most popular are acrylic and epoxy.
Acrylic concrete sealer forms a thin film resin membrane on the bare concrete. It results in a finish that will enhance the look of your concrete and protect it against UV sun damage. It will not only block surface moisture from above but also protect against moisture from below since it penetrates the cement pores. It tends to make floors slippery when wet, so you may consider adding an anti-skid compound to the finish.
Although not as long-lasting as an epoxy concrete sealer, it is less expensive and easier to apply, making it the best choice in most cases. Acrylic is also available as a wet-look sealer which is good for stained concrete projects.
Epoxy concrete sealer is very strong and durable. In fact, it is so tough that it can trap moisture beneath its surface, resulting in eventual cracking and bubbling in the finish. This makes it somewhat more difficult to apply than acrylic sealant. But if your primary consideration is durability rather than appearance, epoxy sealants are a better choice. A concrete shower, for example, may be better to finish with an epoxy sealer.
Other types of concrete finishers include silanes, silicates, and silicones. These are sometimes applied to the bare concrete substrate as a primer for the topical epoxy or acrylic finishes.
How to Polish Concrete Floor to Shine like Marble
Those wondering how to polish concrete without an orbital sander polishing machine will probably not want to hear this. Still, unless you are prepared for weeks of intensive manual labor, the only viable option is to use a power sander.
Fortunately, concrete polishing kits are becoming increasingly common. Plus, several hardware and flooring stores have started to rent out orbital sanders to consumers.
An orbital sander is a sanding machine where the motor turns a rotating disk instead of a belt or drum sanding machine. A more recent improvement in orbital sanders is the random orbit sander. The random orbit sander features a dual rotation of the sanding disk and the driving head. As a result, random orbit sanders have the high sanding speed of a belt sander, combined with the ability to produce a fine, polished finish of a traditional orbit sander.
When polishing a concrete floor, you want to start with 50-grit diamond disks on the machine. As you grind the floor, the disks will slowly wear down, so it is important to check on their condition frequently and replace them as needed.
Wet the floor before you start with enough water to keep the surface of the concrete wet. Slowly push the grinder from behind, walking in straight lines back and forth across the room. When you are done, the floor will be covered in a paste made from water and ground concrete powder. Rinse the floor and inspect it carefully. Redo any sections that you missed, then rinse the floor again.
You will now need to repeat the process, replacing the 50-grit disks with 100-grit disks. Make sure to keep your steps even and deliberate to avoid creating unnecessary swirls or unevenness on the floor. Once you are done with the 100-grit disks, you can further smooth out any imperfections by first using 200-grit disks, then upgrading to 400-grit disks.
Although a standard grinder can easily polish the main part of the concrete floor, it often has trouble reaching corners and getting to the ends of the edges. You will need to use a right-angle grinder to finish the entire floor.
Starting with 50-grit, then upgrading to 100-grit sandpaper, 200-grit, and, finally, 400-grit disks, run the right-angle grinder around the room’s edges, paying special attention to any rough areas that the standard grinder could not reach. Even though the process of polishing a concrete floor can be tedious and time-consuming, you will be left with a beautiful, lustrous floor, knowing how to polish concrete, and the satisfaction of a job well done.