Grinding Concrete

Grinders are typically used to shape concrete surfaces that won’t be visible once the project is installed. We use grinders to remove concrete on the underside of a countertop section  but don’t use them on the top surface.

Grinders are often confused with polishers, but in reality are very different tools.  A grinder, with speeds over 10,000 RPM, is much faster than the 4,000 RPM maximum speed of a polisher.

What You’ll Need
  • Alpha 5″ High Speed Angle Grinder, HSG-125
  • Alpha 4 1/2″ Vexcel Rigid Diamond Grinding Disc
  • Alpha Ecogrinder, ECG-125
  • Alpha 5″ Segmented Grinding Cup
  • Alpha 4″ Grinding and Shaping Wheel
  • Eibenstock 5″ Concrete Grinder

Step 1 – Grinding vs Polishing

Grinding Concrete - Step 1 | CHENG Concrete Exchange
  • Grinding can be thought of as the roughest way to flatten a concrete surface. Polishingis when you take that ground surface to a progressively smoother, shiny finish.
  • When doing pre-cast concrete projects, it’s not usually necessary to use a grinder. Since the formwork is doing most of the shaping, the only place you would need to use a grinder would be on a part of the project that is hidden (like the back side of a concrete countertop).
  • In that case, you need the countertop to be flat on the back, but nobody will see it, so it can be very rough.

Step 2 – Grinding Basics

Grinding Concrete - Step 2 | CHENG Concrete Exchange
  • Dry grinding is extremely dusty, always wear a particle mask. Don’t grind indoors unless you have proper ventilation.
  • Most grinding is done while the concrete is still in the formwork. The walls of the form are used as a guide to make sure the piece is being ground flat.
  • You can use a high speed angle grinder with a concrete grinding disc. Some of these discs are contoured, so you can shape down into the concrete instead of just grinding it flat.

Step 3 – Grinders and Grinding Cups

  • Some are contoured.
  • Most concrete grinders will hook up to a vacuum for dust collection.