To sand down concrete, remove any coating, seal the cracks and joints with an epoxy filler, attach metal-bonded diamond discs to a grinder, and sand the surface of the concrete. Start with a 30- or 40-grit diamond disc, and slowly increase the grit until you reach the desired finish.
- Remove the concrete coating
If the concrete is coated, attach a 16- or 20-grit metal-bonded diamond disc to a floor polisher or handheld grinder. Sand off the coating.
- Fill in the gaps
Apply a semi-rigid filler such as an epoxy filler. Let the filler cure before proceeding.
- Sand the concrete
Attach a 30- or 40-grit metal-bonded diamond tool to the grinder, and sand the surface of the concrete. Once the entire surface is sanded, change the diamond disc to an 80-grit one, and sand the floor again. Repeat the process with a 150-grit metal-bonded diamond tool.
- Make the concrete denser
Apply a specialty chemical hardener to the concrete.
- Polish the concrete
If you want, continue upgrading the sanding discs until you achieve a glossy finish. Switch from a metal-bonded disc to a resin-bond one. Attach a 100-grit tool to the grinder, and sand the surface. Repeat the process with 200 then 400, 800, 1,500 and 3,000 grits.