Concrete is considered hard when it tests above 6000 PSI and above a 7 on the MOHS scale.
For hard concrete, the initial cut is very difficult and cutting diamonds have a hard time penetrating the concrete and grinding it. When grinding hard concrete floors, it’s imperative you use a diamond with a soft bond.
To improve production rates, use a soft-bonded diamond with a smaller surface area. In extreme cases, wetting the concrete in front of the grinder can also increase production rates and help the diamonds cut and stay cool.
When using large machines with adjustable speed controls on hard concrete, the recommended operating speed on a scale of 1-10 is as follows. Start around a 3 for the courser grits and gradually increase speed with each step until around 7-8 on your fine grits.
1. 30 Grit Metal
Note: Skip this step if the floor doesn't have topical curing chemicals.
2. 50 grit soft BSD Polishing Diamond or soft Premium 8 Segment Diamond
3. 100 grit soft BSD Polishing Diamond or soft Premium 8 Segment Diamond
5. 400 grit BSD Polishing Diamond
6. 800 grit Blue Star Diamond Dry Resin
7. 1500 grit Blue Star Diamond Dry Resin
8. Burnishing Pads
1. 60/80 Grit Metal
2. 100 grit soft BSD Polishing Diamond or soft Premium 8 Segment Diamond
4. 400 grit BSD Polishing Diamond
5. 800 grit Blue Star Diamond Dry Resin
6. 1500 grit Blue Star Diamond Dry Resin
7. Burnishing Pads