You’ve finished polishing a concrete slab – it’s got a smooth finish and a beautiful glossy sheen – just like what the client requested. But three months later, the client is calling because the slab looks dull and drab. What happened? If you’ve polished concrete in the past, you probably know the answer – pinholes. Pinholes are the tiny cavities and holes on the very surface of the concrete that are nearly invisible upon first glance. However, pinholes will make a polished surface look dull because they interrupt the reflection of light on the surface. Over time, they hold dirt and debris, making the slab look even worse.

The solution to pinholes is to fill them in with grout during the polishing process, but hand grouting can add hours of time (and cost) to the project. Instead, of grouting by hand, we’re sharing how to use your concrete grinder to grout your pinholes and get a better result.

Grout Pans from STI

With grout pans from STI, you can get a near flawless finish in less than half the time that it takes to do the project by hand. These small, concave discs are made of stainless steel and attach to your concrete grinder with Velcro, just like regular diamond pads.

Here’s how to get the best results to eliminate pinholes with your grinder and grout pans:

  • Apply a coating of epoxy with a trowel, using just a light coating over the slab. Be sure to press the epoxy in so it fills the holes while pressing any air that’s in the voids up to the surface.
  • Sprinkle ground marble, called calcium carbonate, over the grout in a thin, even layer. Note: Do not use concrete dust from your dust collector as this may have dirt, debris, and other impurities that will ruin the coating.
  • Outfit your grinder with the grout pans and add the pocket weights to the top.
  • Run at 25 Hz and slowly go over the epoxy and calcium carbonate to push the coating into the pinholes. Note: Do not use your dust collector as that will pull up the calcium carbonate.
  • Cure for 8 hours, then use your grinder at 40 Hz with a grinding pad and water to remove excess epoxy and any scratches left from grout pans
  • Remove slurry from the slab, clean, and allow to dry.
  • Add a layer of concrete densifier with a microfiber wet mop.
  • Begin dry polishing of the slab.

By following these steps, you’ll get a smooth, even appearance that’s free from pinholes and the dulling they cause.

Order Grout Pans and More Today

At Buy Manufacturers Direct, we carry everything you need to get a beautiful, long-lasting polished concrete slab. To learn more about our products or get a quote on gear, reach out to us today at   (815) 472-9749 or by filling out our contact form to get started!