Did you know that polished concrete floors are the most environmentally conscious flooring solution available? The reason is that the polishing process involves honing the existing concrete down over and over again with lighter and lighter diamond blades until the floor reflects light with a nice shine.
This sustainable flooring solution takes between 5, and 7 passes with a concrete grinder to get it just right. A polished concrete floor makes a room feel bright and lively. It’s also easier to clean and maintain than a lot of other flooring systems. Here is a step by step process to polish concrete floors.
How To Polish Concrete Floors: Step-By-Step
Step 1 - Use The Right Materials
Ensure you have an industrial grinder and enough diamond blades with the right grit levels to sand and hone the concrete surface.
Tools You Need:
- Concrete grinder
- Concrete sealer
- Burnishing pad
- Wet dry vacuum
- MOHS hardness pick set
- Safety clothes and handsets
Step 2 - Clean and Patch the Surface
Start off by cleaning the entire floor surface. This step involves a simple cleaning of the floor. Make sure there is no rubble or debris. In this step, you should also inspect the floor for stains or other floor imperfections, which could become a problem later. Get everything off the floor and start preparing your machinery and dust vacuum. If you encounter stubborn stains, try to use surface cleaner.
Once you're done cleaning and before you polish the concete, inspect the concrete floor for damaged areas. Be sure to scan for any bumps or divots. Mark them to make sure you don’t run over them with your grinder. Some of these areas will need to be hand grinded if they are elevated initially, but divots need to be filled before the grinding process starts.
Once you find issues, fill cracks and apply a polishable overlay. This is essentially applying a concrete-like ardex to the floor surface to fill in the cracks and divots. You let the overlay dry, and then you can polish it just like the rest of the floor. Sweep the floor clean from debris after the patches have cured. Polishable overlays are not cheap. This step is the difference between having a level concrete floors versus those that look bad after all the work you do. Note that if there are a lot of divots, you will have to apply a polishable overlay on the entire floor. Otherwise, it will look patchy, and no one will be happy with it.
Step 3 - Test The Hardness Of The Concrete
The concrete floor hardness is tested using the MOHS (measurement of hardness scale) hardness before using a diamond grinder. Choose representative areas of the floor, hold #9 picks like a pencil, apply some pressure and draw roughly 2 inches (5.1cm) pencil lines on the concrete. Take a glance and feel if there is a scratch. Work your way through the pick numbers until you reach a pick that doesn’t leave a scratch (#8,#7, and more). If for example, the #6 pick scratches the concrete, but #5 doesn’t, the concrete has a MOHS of 5.5
Step 4 - Grind the surface with a grinding disc.
Based on the MOHS test purchase, rent a grinder that precisely suits soft, medium, or hardened concrete. The grinding discs must be metal bound and contain diamond blades. You need to protect yourself before you start grinding concrete. Put on thick gloves, dust mask, safety goggles, and earplugs, then attach the diamond blades, and get to work.
The idea here is to start with thicker blades. That means you will take off more of the surface of the concrete and go over the entire concrete floor. You are going to repeat this polishing process with finer and finer diamond grits and polishing pads. You will literally polish concrete down into a shine. Start from one corner of the floor to the other, and remember to remove stains using a 40-grit grinding disc. Go slowly and work over the surface until you see some notable change.
Once you grind with 40-grit, repeat concrete grinding using 80- grit through 400- grit discs. Pass over the floor with each grit working perpendicular to your last pass; each disc will buff away scratches created during the previous pass.
Then make the final grinding pass with a 3000-grit disc. Work over the entire concrete flooring, and move in a diagonally opposite manner. The grit in this disc will polish the surface and restore its high-gloss appearance. Vacuum all dust and debris off the concrete surface before you buff the concrete.
Step 5 - Spray Densifier After Grinding
Coat the whole floor using a densifier, a liquid chemical hardener, per its instructions. It makes the concrete less permeable and less powdery.
Step 6 - Buff and Seal the Surface
At this point, use a burnishing pad and apply a concrete sealer. A burnishing pad makes the floor smooth. It’s soft, unlike the diamonds used to grind the floor. The floor should be relatively smooth at this point, since the burnishing pad is what makes it pop and reflect light. Once you are done with the pad, apply the water-based or solvent-based concrete sealer and spread it evenly.
Sealers help protect concrete floors from grease, dirt, and other stains. The amount of grinding you do and the type of sealer you put on the floor dictates how the floor will look. You can use a densifier/sealer to get a matte finish, wet finish, or shine. Make sure to apply the sealers during dry conditions.
Apply a second sealer coat after 2-4 hours, wait for it to dry, and burnish to give the floor a final smooth and glossy finish. Give the floor 24-72 hours, after which the concrete floor will be ready to use. At this point you're finished with this polishing job.