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When fitted with the proper attachments, an angle grinder can be used to smooth, polish or level concrete surfaces. You can use a wet or dry angle grinder. With the proper supplies, protective equipment, and step-by-step instructions, this job can be safely and easily completed by non-professionals.
Using an Angle Grinder to Grind Concrete
Before starting, familiarize yourself with some of the dangers unique to grinding concrete, and take steps to protect yourself. Then, assemble the appropriate supplies and accessories and prepare your work surface. Finally, follow the grinding instructions below to create a smooth, level, and/or polished concrete surface.
Preparing Concrete for Grinding
- Never grind a dirty surface. Use a brush or broom to collect any loose dust or dirt. A wet rag or mop should be used next. If the concrete is excessively dirty or grimy, washing with a power washer may be necessary to prepare the surface for grinding.
- Assemble the tools and accessories you will need. These include:
- Angle grinder
- Diamond cup grinding attachment
- Eye protection
- Hearing protection
- Knee protection (if kneeling)
- If you are using a dry grinder, you will also need:
- Dust shroud with vacuum hose attachment
- Vacuum with compatible hose
Avoiding Concrete Debris
Grinding concrete releases silica particles. If inhaled, these can cause serious injury along the respiratory tract, known as silicosis.To avoid the potential health risks, you will need to use a respirator.
Respirators are dust masks that have been rated based on their ability to filter out airborne particles. An N95 rated respirator with a proper fit will block 95% of particles from reaching your airway. A P100 rated respirator is an even better choice, as it should block 99.9% of airborne particles.
You must wear a respirator at all times while grinding concrete, even if you use a wet angle grinder. If using a disposable mask, make sure to check the manufacturer’s specifications about how long it can be used.
- Fit the angle grinder with a diamond cup wheel. A low-grit cup wheel will quickly and roughly remove excess concrete. To achieve a smooth or polished look, switch to a higher grit cup wheel. To reduce the risk of serious injury, the maximum RPMs listed on the attachment must meet or exceed the RPM of your grinder.
- Adjust the guard of the angle grinder so that it is between the grinder and your face. Connect the angle grinder to power. With both hands on the angle grinder, turn the power on. Check the disk integrity by turning the angle grinder on and allowing the disc to spin freely for 60 seconds. If the disc wobbles, disconnect the grinder from power and double check that the clamping flange is properly tightened against the disc.
- Pass the cup wheel over the surface of the concrete. Avoid holding the angle grinder still or leaving it too long in one spot, as you may remove more material than you intended. Instead, grind in a circular motion, with each circle overlapping the one before it. This will help you achieve an even grind across the entire surface of the concrete. Different angle grinder attachments can be used to create patterns on concrete.
- Do not add additional pressure or weight to the power tool. Keep both hands on the angle grinder for safety and control. Stop grinding immediately if the angle grinder feels hot to the touch.This is an indication that it may be overheating, which could cause irreversible damage to the machine.
- If your angle grinder overheats, stop grinding. Remove the disc from the angle grinder. Clean the intake vent. If the vent is clogged with dust, the cooling fan will not work properly When the vent is clean, turn the angle grinder on. The built-in cooling fan will pull air over the surface of the motor, returning it to a safe operating temperature.
- Check the surface of the floor for evenness and regularity. Switch to a higher grit disc if a smoother surface is required. If you are grinding dry, you may need to remove the dust shroud in order to reach edges and corners. You should save these tasks until the end of the grinding process and complete them all at once. This will limit the amount of exposure to silica dust.
- When you are satisfied with the surface, turn off the angle grinder. Wait for the disc to stop spinning, then set it down and disconnect it from power. Allow the dust to settle. Use a wet cloth or mop to clear the surface of dust.
Learn how to drill into concrete with our complete guide.
Concrete Grinding Tools
When grinding a small area of concrete or a vertical surface, a handheld angle grinder is the best choice. For grinding large horizontal areas, a floor grinder will save time and energy.
Wet Angle Grinder
A wet angle grinder is designed to be used with water cooling the surface of the blade. This extends the life of the grinding disc, which will not wear down as quickly. It has the added benefit of dampening down the concrete dust created by grinding.
Not only will this keep your work area cleaner and the angle grinder vent free from debris, it will also decrease the risk of inhaling dangerous silica particles. If you have a lot of concrete to grind, a wet angle grinder is better than a dry angle grinder
Dry Angle Grinder
If you already own a dry angle grinder, you don’t need to buy a new tool just for this project, just some accessories. You will need to attach a dust shroud to the machine.
A dust shroud is a plastic case that covers the area around the grinding disc. It is then connected to a vacuum hose. The shroud keeps dust from spreading around your work area by directing it into the vacuum hose, where it is then contained in the vacuum.
Cutting through concrete pavers for your outdoor patio or block wall is a great use of a dry angle grinder.
An angle grinder is best used for small to mid-sized areas, such as stairs, benches, pavers, or walkways. If you need to smooth a large surface area, such as a floor, you can certainly accomplish this with an angle grinder. However, due to the small surface area of the grinding disc, it will require hours spent on your knees.
A walk-behind concrete floor grinder operates similarly to an angle grinder but on a much larger scale, and without requiring you to bend over. You can rent a concrete floor grinder from most major home improvement retailers.
Concrete is unique because of how dense the material is. Unlike with cutting more porous material like brick, picking a diamond cup wheel is essential.
An angle grinder is well-suited to small and mid-sized concrete grinding jobs. Either a wet or dry angle grinder can be used to grind concrete. Protect yourself from inhalation of dangerous particles with the proper equipment.