Ground concrete is the lowest category of steps of a processed concrete surface. Any grit abrasive from approximately a 50-grit resin and below is considered a grinding step. A ground concrete surface has a flat appearance with no or very slight reflection and many at times have a low sheen. The next category of steps above ground concrete in the processing system is the Honed concrete. Any grit abrasive from approximately a 100-grit resin to a 400-grit resin is considered a honing step. A honed concrete surface has a matte appearance and slight clarity of reflection that has a low, medium or high sheen. The highest category of steps of processed concrete is the polished concrete. Any grit abrasive from approximately an 800-grit resin and above, typically to 1,500 or 3,000 grit, is considered a polishing step. A polished concrete surface has clarity of reflection like a mirror and has a glass-like finish.
We heavily recommended that you do not skip grit in the processing sequence, and when transitioning from metal bonded abrasives to resin bonded abrasives the first resin bond grit abrasive used must be one grit lower than the last metal grit abrasive used. In rare situations, you may be able to skip a grit or not drop back a grit.
Concrete is usually ground dry for convenience because it can be done with fewer people than wet grinding, although a filter-equipped vacuum is needed to capture the fine dust produced. Of course, concrete can also be ground wet in which case you don’t need to use a vacuum. Fine concrete dust contains silica which is very harmful to the lungs hence; all effort should be made to avoid breathing concrete dust.
The grinding process involves;
Acquire a concrete grinder. You’ll need to use a specialized tool to grind concrete; you can usually rent concrete grinders from most hardware stores making sure that it is cost effective.
Wear protective gear. Before handling the grinder, you should prepare yourself by wearing a dust mask, gloves, safety goggles, protective shoes, helmet, and ear plugs.
Concrete surface preparation.
- Determine surface hardness to select the correct metal bond diamond abrasives to use.
- Clean it up by Preparing a solution of warm water and household detergent, then scrub the concrete thoroughly using that solution and a bristle brush. You might need to use a stronger cleanser for especially stubborn stains or mold. Hydrogen peroxide, ammonia, and TSP are standard options but do not mix these chemicals.
- Repair any cracks present using a specialized concrete crack filler. Follow the instructions on the package to mix and apply the filler
Grind the concrete with the coarsest disc. Before you start grinding make sure that you think about the pattern you are going to do and how the vacuum hoses and power cords will affect your path. Follow the instructions that come with your grinder to determine the proper way to attach discs and power the machine. If you need to remove sealer, stains, or other contaminants that wouldn’t wash off, start with a 40-grit grinding disc. Note that these discs must be metal-bonded diamond discs. Non-diamond discs will not be hard enough to grind down the concrete. You will need to use at least two or three more grinding discs. Choose discs that are progressively higher (less coarse) in grit-size. The exact grit sizes may vary depending on the hardness of your concrete. As a general guideline, however, follow the 40-grit disc with an 80-grit disc. To obtain a clean, crisp look of the concrete surface at a 200-, 400- and 800-grit resin, perform each grit and refine to its maximum potential
Apply densifier in the middle of the process; spray liquid chemical hardener over the surface to help solidify the concrete if necessary, the concrete would dictate at what grit a densifier would be applied. Three types of densifiers that are most commonly used include – sodium, potassium, and lithium. Each manufacturer has specific instructions and directions for the application.
Vacuum any debris. After you finish all of the grindings, you should vacuum as much debris as possible. Note that some concrete grinders come with their vacuum. In these instances, use that vacuum instead of a separate shop vac.