How to grind concrete

How to grind concrete

We’ll show you how to grind concrete in this post. There are many reasons to grind concrete. For repairs, renovating concrete and for decorative purposes. Concrete can be ground to a polished finish for decorative and maintenance reasons or ground roughly to make a better key for renovating your concrete.

See our renovating concrete post here!

Types of concrete

There are 2 types of concrete for grinding, new and old concrete. Grinding new concrete is best done by professionals and in consultation with your concreting professional and concrete supplier.

The new concrete should have properties that will deliver the best results for grinding. Plus you can add specific stones or objects and colors to your new concrete to enhance the ground concrete.

Old concrete will be a bit of a Pandora’s box, not knowing what will be revealed by grinding the concrete. You may not be able to get a polished finish on old concrete, but the blemishes and other issues will add character to the finished job.

Concrete grinders can be used either wet or dry depending on the results desired.

A dust removal system plus PPE should always be used when grinding concrete using the dry method.

Types of grinders

There are several types of concrete grinders available, from hand held grinders to large planetary grinders.

planetary concrete grinder
planetary concrete grinder

For general grinding a terrazzo grinder or a single cup grinder will do a decent job. Larger planetary grinders are used by professionals for large jobs with better results. To get the edges and corners of concrete slab ground down, hand held grinders may be used.

single disk concrete grinder
single disk concrete grinder

All concrete grinders use diamond cutting disks or wheels. To get a polished finish the diamond wheels or disks are range from coarse to very fine for the final passes.

The grade of diamond cutting disks used need to match the type of concrete being ground. For hard concrete you need a soft compound for the diamonds and for soft concrete you need a hard compound for the diamonds. If your not sure if your concrete is hard or soft, you can test it. Another way of determining if your concrete is hard or soft is to assess the concrete when you start to grind it. If the grinder isn’t doing much to the surface you probably have the wrong diamond compound for for grinding diamonds.

Using a concrete grinder

For the DIYer using a single cup concrete grinder is much like using a floor polisher. However when starting a concrete grinder always lift the grinding disk of the ground and lower onto the surface once it is started. Then grind in a sideways back and forth motion and pull back as you grind, never leave the grinder going in one spot.

To get an even surface may require that you grind one way and then at a 90 degree angle to the first pass. You will only achieve a coarse finish with a single disk grinder. These grinders are good for grinding concrete that is going to be resurfaced.

Always turn on your dust extraction system before starting your grinder if you are dry grinding. You may have to empty your dust extractor several times when grinding concrete.

Unless your grinder will grind up against the walls or edge of your concrete, you will need to use a hand grinder to finish the edges.

Dust extraction

Your dust extraction system can range from a shop vac to a dedicated dust extraction system. For small jobs a shop vac will suffice, use of a separator will help save your shop vac from an early death when concrete grinding. A professional dust extraction system will set you back a couple of thousand dollars, so unless your going into the concrete grinding business you won’t be needing this.

concrete grinding

Clean up

You will need to clean up your concrete surface after grinding to remove any dust or debris. Vacuum up as much dust as possible and then mop several times to remove any fine dust left from vacuuming.

If you use the wet grinding method , you will need to mop up the slurry and then re mop several times to remove all slurry produce when grinding.

After cleaning up you may need to repair parts of your concrete before you proceed to the next step of your concrete grinding project. Fill any cracks or holes and re grind these areas to match the surrounding surface.

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Finishing ground concrete

There are several options to finish your concrete grind project. You can resurface the concrete with a thin layer of resurfacing compound, or use concrete sealer to put a clear wet look on your concrete. Or you can keep grinding using finer and finer grade diamonds for a polished finish.

How you finish your concrete depends on what type of surface you want and whether the concrete is in the elements outdoors or under cover. Some finishes are not UV stable and are only suitable for interior use.

Looking at these options on how to grind concrete should help you determine if you are capable of grinding your own concrete or not. Small areas such as garages are good size grinding projects for DIYers, anything bigger should be given to professionals to complete.

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