How to Use an Angle Grinder to Smooth Concrete: (Complete Guide)

Regardless of how skilled you are with installing concrete, you can never achieve the desired level of smoothness and flatness required in just one go. After installing the concrete, you will need to smoothen or finish it so the concrete slab has a clean and smooth finish. The problem here is that it is difficult to smoothen concrete when it’s wet.

You need to let the concrete cure (or dry) for a while before you can smoothen it. If you smoothen the concrete when wet, you will still end up with an uneven surface because the curing process will affect the shape and structure of the concrete.

Concrete surfaces are one of the hardest and toughest to alter especially when dry. So how do you smoothen a surface as hard and coarse as concrete?

There are different methods to smoothen a hardened concrete surface but using an angle grinder is at the top of the list. An angle grinder equipped with the right disc will give you a clean, smooth, and flat finish on the concrete.

So, how to use an angle grinder to smooth concrete? What type of disc do you need with an angle grinder to smoothen concrete? And why should you smoothen concrete? You see there is a lot more to know about smoothening concrete. This post will introduce you to all you need to know about smoothening concrete with an angle grinder, so let’s get on with it.

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What Tools Do You Need to Smoothen Concrete With an Angle Grinder?

You need the following to smoothen concrete with an angle grinder.

  • An angle grinder. Angle grinders come in different size-variations. Depending on the size of the concrete you want to smoothen, you can get a 7-inch angle grinder, a 9-inch grinder, or the smaller 4-inch or 4½-inch angle grinder. Angle grinders also come in battery-operated and corded models so get the one that fits your budget. I will recommend getting a 7-inch battery-operated angle grinder. With this, you don’t need to worry about power supply or tripping over wires while working. The battery-operated model is also more mobile.
  • A pair of work gloves
  • A pair of safety goggles
  • A respiratory mask
  • A diamond smoothening disc. I will recommend a 24-grit diamond abrasive disc.

What Type of Disc Do I Need to Smoothen Concrete With an Angle Grinder?

You need to use a diamond disc or polishing pad to smoothen concrete. Angle grinders have a plethora of available discs that can be used with the tool. A grinder is a multi-purpose tool that can be used for cutting, cleaning, smoothening, and sanding. The task you want to use the tool for will depend on which disc you buy or rent. For smoothening concrete, you need a diamond disc.

Regular disc pads wouldn’t do much on concrete. It wouldn’t do anything other than just damage the disc itself.

For concrete, you need a highly efficient diamond smoothening disc or diamond polishing pad for angle grinders. The diamond disc will remove scratches and smoothen uneven surfaces easily and quickly. The discs can also be used for both dry and wet smoothening or sanding. Diamond discs are already recommended for smoothening concrete and even metal.

The disc isn’t embedded with real diamonds. The term is just to point out the fact that these discs have very coarse abrasive materials which make them suitable for concrete.

You need to ensure you buy or rent a diamond smoothening or sanding disc and not a diamond cutting disc. The difference between both discs is in the name. The downside to the diamond smoothening disc is that it is a bit more expensive than regular discs.

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How to Smoothen a Concrete Surface With an Angle Grinder

Using an angle grinder can be an easy task and it can be a difficult one too depending on how much experience you have with using the tool. The steps below have been carefully explained to make the whole process easier even if you have no prior experience with using an angle grinder.

1. Put on Your Safety Gear

The first thing to do is to ensure your safety. Put on your work gloves, your respiratory mask, and a pair of goggles.

While smoothening concrete, you are at risk of different injuries if proper care isn’t taken. The gloves will protect your hands from cuts and bruises. The respiratory mask will protect you from dust and the goggles will protect your eyes from small stones and debris.

2. Clean the Concrete Surface

You need to use a damp cloth to wipe off any dust, dirt, or debris from the concrete.

3. Attach the Diamond Disc

You need a diamond smoothening disc to smoothen the concrete. Chances are you do not have a diamond disc already installed. The first thing to do is to unplug the angle grinder or remove the battery. Then press the spindle-lock button located on the top of the angle grinder.

The spindle-lock button ensures the existing disc in the angle grinder is locked firmly. The next thing to do is to use a wrench to remove the clamping flange. The clamping flange is a metallic ring-like object that holds the disc in place.

When you have loosened the clamping flange, take out the previous disc. You might use this opportunity to clean the inner parts of the angle grinder. After cleaning, attach the diamond disc to the angle grinder. You need to be mindful of the abrasive side of the diamond disc.

The abrasive side should be installed facing the outward direction. There are signs on the disc to show you how you should attach it to the angle grinder. After attaching the diamond disc, screw in the clamping flange you took out earlier and ensure the disc is firmly locked in place.

4. Power-up the Angle Grinder

After fixing the diamond disc correctly, you should power-up the grinder. This means you should fix-in the battery or plug-in the wire into a wall outlet or socket.

When that is done, you can test run the grinder. To test run, switch on the angle grinder and press or pull the trigger button. It should work just fine.

5. Start Smoothening

If the grinder works well, you can start smoothening. There are two methods for smoothening concrete. You can use the dry method or the wet method.

The distinction between both methods is the use of water. For the dry method, you just need to place the already attached diamond disc on the concrete surface and press or pull the trigger button. The disc will start spinning and you will need to move the grinder in a circular motion slowly from side to side to smoothen the concrete.

For the wet method, you need to pour water on the concrete surface while smoothening the concrete. The wet method has been argued to bring a smoother, cleaner, and finer result than the dry method. This is because of the water on the surface which serves as a lubricant. The water allows the grinder to move easily as opposed to the dry method.

Asides from the smoother finish the wet method brings, the wet method also reduces the risk of injuries from dirt and debris. With the dry method, there is usually a lot of dust and dirt flying around.

With the wet method, the dust is reduced drastically and there is also minimal noise as opposed to the dry method that creates a lot of noise. So the wet method might be your best bet. You just need to ensure the concrete is constantly wet but not too wet.

You should hold the angle grinder with both hands for maximum grip. Also, do not press the disc on the concrete. Just ensure the disc comes in contact with the concrete and move it around.

6. Wipe the Surface With a Rag

While smoothening, you should constantly take a break to wipe the concrete surface and check the level of smoothness. If you figure out you have the desired level of smoothness on the concrete, you can stop smoothening. If you feel the concrete isn’t smooth enough, you can continue the task.

As a precautionary measure, do not smoothen a concrete too much. Just do a bit and if required, you can go on to polish the concrete surface later.

If you smoothen the concrete too much, you will expose the inner components of the concrete and that can damage it. When you are done, you should give the surface a clean wash and let it dry

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Why Should I Smoothen Concrete?

Smoothening concrete automatically improves the look and finish of the concrete. Concrete that requires smoothening or finishing is usually installed indoors such as concrete slabs and concrete tables.

For concrete installed outdoors, smoothening the surface might not be necessary. Concrete installed outdoors needs to be slip-resistant and should be able to cope with minimal cleaning, so smoothening the concrete isn’t needed.

Indoor concrete on the other hand need to be smoothened to give it a fine appearance. Asides from improving the beauty and appearance of the concrete, smoothening the concrete will also:

  • Improve the lighting effect on your concrete. When the concrete is properly smoothened and finished, the rays of the sun and light in the room will reflect on the concrete making it seem brighter and more radiant.
  • Give your surface a more expensive appearance. Smoothened concrete usually looks much more expensive than regular concrete.
  • Make your surface more stain-friendly. It would be easier to get stains off smooth concrete surfaces.
  • Improve the durability of your concrete

Pro-tips to Follow When Smoothening Concrete With an Angle Grinder

  • Use the right disc. For this task, you should buy or rent diamond smoothening disc or diamond polishing pads for angle grinders. You can also read the information on the container to be sure the disc can be used on concrete.
  • Be mindful of the wires. If you are using the corded angle grinder, be careful not to trip over wires. You also need to be mindful of the connection of the wire especially if you are using the wet method so you do not risk electrocution.
  • Do not press the disc on the concrete. This can damage both the disc and the concrete
  • Get professional help. If you aren’t too sure you can do it, get help from a professional.
  • Keep a safe distance from the surface while smoothening so small stones do not hit you in the face
  • Always put on your safety gear

So there you have it. I’m sure you now know how to smoothen concrete. If you have any questions or comments, kindly leave them below and I’ll attend to them as soon as possible. Have a nice concrete-smoothening experience.

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