Grinding Concrete with an Angle Grinder (A Complete Guide)

In this guide we will provide you with instructions on how to grind concrete using an angle grinder. We will also discuss with you the advantage and disadvantage of using an angle grinder and projects you can use. Furthermore, we will give you tips on how to grind your concrete effectively.

Grinding concrete with an angle grinder

Do you have uneven concrete slab and in need of a tool that will level your concrete? An angle grinder is the best tool for this purpose. Angle grinder can be used for various purposes aside from leveling your concrete. It can be used also to smoothen and polish your concrete by grinding it down and can be used to remove floor adhesives and paint.

Here are the common uses of angle grinder for your concrete:

  • Flattening uneven flooring removing high spots or ridges before installation of your flooring.
  • Grinding down thin-set and other hard coatings.
  • Thinning-out cracks and heaves to reduce tripping hazard in your concrete floor.
  • Clear-out sealed concrete surface for adhesion of thin-set, epoxy, or other adhesives in your concrete.

Parts of Angle Grinder

Due to the functionality of angle grinders in many situations, it requires a variety of accessories to support the grinder’s efficiency at cutting, smoothening, cleansing, shaping, and grinding.

Here are the essential grinder accessories:

  • Cutting Discs

From the name itself, cutting discs are used for cutting through objects like metal and concrete. The sharpness of this accessory facilitates cutting from wheels to glass.

  • Sanding Discs

Sanding discs or flap discs are used to brush-up, shape and cleanse surfaces. This disc is usually attached to orbital sanders to smoothen surfaces by abrasion with sandpaper. Sanding pads are placed to a plate attached to the grinder. These sanding pads have distinguishable abrasive qualities of the grit. Flap discs are expensive compared to other accessories and easily worn off.

  • Grinding Discs

Grinding discs are more harsher tools used to remove rust or corrosive metals from vehicles and smoothen concrete surfaces. Grinding gears are very cheap for limited uses due to its slightly thicker grit flap.

  • Wire Brushes

Wire brushes are used to remove paint or cleanse rust from all surfaces. This has the same application with grinding discs but more delicate and works equally on uneven materials. The wire brush filaments spin across the surfaces which prevents damage to the surfaces while cleaning.

  • Synthetic Non-woven Flap Discs

Synthetic non-woven flap discs are almost similar to the design of flap discs, but their constitution is diametrically different. This accessory contain polymer abrasive instead of particulate pad and highlights the gradation in the polymer density.

How to Smooth Concrete with an Angle Grinder?

Materials you’ll need:

Step-by-step instructions

Here’s the step-by-step instructions on how to smoothen your concrete floor:

Step 1. Clean the floor area.

Clean the floor area by vacuuming or mopping the floor. You may also use a pressure washer to effectively clean the surface, especially the edges.

Step 2: Prepare an extension wire.

Prepare an extension wire for your wet/dry vacuum and angle grinder.

Step 3: Attach your dust shroud to the angle grinder.

Attach your dust shroud to the angle grinder. Make sure that the dust shroud is fitter and secured to the grinder by tightening the clamp fitting on the suction hood. This will lock the dust shroud in place.

Step 4: Connect the vacuum nozzle.

Connect the vacuum nozzle to the vacuum adapter on the dust shroud similar to wet/dry vacuum inlet.

Step 5: Fit whichever wheel you want to use to smoothen your concrete surface.

Fit whichever wheel you want to use to smoothen your concrete surface, preferably start with diamond polishing pad. Make sure to attach this accessory while the angle grinder is disconnected to the power source.

Step 6: Wear your safety gears.

Once all accessories and other tools are connected and in place, wear your safety gears. Fit your masks, eyeglasses, gloves, knee pads, and earplugs.

Step 7: Start smoothen the edges.

You can now smoothen the concrete surface area using an angle grinder. Start the edges around the perimeter of the room.

Step 8: Smoothen the inside perimeter of the floor area.

Once the perimeter edges are smoothen, work inwards manipulating the angle grinder in circular motions. Maintain circular motion to achieve a greater degree of consistency.

Step 9: Smoothen untouched section.

You will notice an untouched section  of concrete around the perimeter edge, this is due to the dust shroud plastic lip obstructing the grinding wheel from smoothing the surface closest to the wall. To smoothen this section, remove the dust shroud from your angle grinder and run through these leftover sections.

Advantages of using Angle Grinder

Angle grinder was originally designed for grinding down and smoothing out metal welds by positioning the rotating blade at an angle, but because of this mechanism it had been used for a wide range of applications with just the right balde. Its application includes cutting concrete, bricks, metal, plastic and more. The tool is also small, mobile, and relatively cheap to buy, thus, buying one is truly not a waste of money.

For concrete applications, angle grinders are utilized for decorative concrete, whether used for improving stamped concrete removing stubs and seams, polishing concrete countertops, engraving, or even freehand scoring.

Disadvantages of using Angle Grinder

Despite its versatility in terms of application, angle grinder isn’t always the best tool for a specific project. Some of its disadvantages are listed below:

  • Efficiency. Angle grinders wear their diamond grinding disc down quickly when cutting concrete. Since common applications of angle grinder are for dry use, they cannot be cooled down using water, but there are angle grinders in which application is specifically for concrete, these grinders come with water attachments.

Some professionals used a walk-behind concrete floor grinding machine that uses water  instead of angle grinder because this is better for maintaining the diamond wheel cool and provides better efficiency in grinding concrete.

  • Size. Commonly, angle grinders use blades up to five or seven inches in diameter. This tool’s dimension limits the span of your angle grinder, thus, taking it a long time to level a concrete floor.
  • Comfort. If an angle grinder will be used instead of a walk-behind concrete floor grinding machine, you need to be on your hands and knees while accomplishing a job.

Applications of Angle Grinder

There is a wide range of applications of this concrete floor grinder. Angle grinder not just for the purpose of smoothing concrete surfaces. Projects such as polishing the concrete of your sidewalks or garage floors, bench tops, sculpture, or walls can also utilize angle grinders with the right shrouds and accessories.

Angle grinder is best suited for small to medium-sized tasks. The sizes of this tool determine which application it is best suited. The tool’s blade ranges from 4 ½-inch to 9-inch. Usually tools of 4 ½-inch and 5-inch models feature high speeds up to 11,000 rpm is suited for grinding off stubs from hardened concrete while bigger models ranging from 7-inch to 9-inch blades are more powerful tools that can be used for cutting joints. This dimension has lower speeds and higher torque providing deeper potential for cutting purposes. Harbor freight has a great selection of heavy duty, cordless and corded angle grinders to fit your budget and the demands of your project.

Conclusion

There are many applications of angle grinder that can be used besides from grinding concrete. This involves the application of smoothing concrete surfaces, cutting slabs and other uses. Doing projects involving angle grinder must be done with consideration of safety. 

For any questions and suggestions about this article, please feel free to submit your thoughts in the comment section below.

FAQs: Grinding concrete with an angle grinder

How do you cut concrete slabs with an angle grinder?

Measure the width of the concrete slab you want to cut and mark them. Wear your safety gears, you should wear at least the eyeglasses, marks, and gloves. Using an angle grinder, run through the concrete slab for at least 3 times or more depending on the width of your concrete slab. Tap the part of the slab where you run through your angle grinder to the edge of a concrete block. Take note that this method is applicable only for thin slabs about 1-2 inches concrete slab.

Can I use a metal grinding wheel on concrete?

Metal-cutting wheels contain either zirconia or aluminum oxide. Wheels intended for masonry use require silicon-carbide abrasive since particles are sharper and harder, thus it can effectively cut concrete and other masonry surfaces. Softer wheels of metal-cutting wheels would simply gaze over brought by abrasive particles wearing down instead of fracturing.

How do I choose a diamond grinding wheel for concrete?

Depending on the purpose, a type of diamond grinding wheel should be chosen appropriately. There are two kinds of concrete grinding: coarse grinding and polishing. Diamond cup wheels that have soft bonds and high diamond hardness of 35 to 50 grit is good for initial coarse grind. Hard diamond bonds are being used for polishing and are attached with polishing discs.

How long do grinding wheels last?

It was recommended by Saint-Gobain the surface grinding wheels be used within 2 years from the date of manufacture. This recommendation is considering that the wheels are stored in ideal conditions.

How do you clean concrete after grinding?

You can clean the concrete by power washing to remove any hidden dirt and to get rid of grinding dust. The concrete can then be sealed, you can use a water test to determine if it is ready for sealing. This water test involves dipping clean water to the concrete to determine the porosity of the slab and how readily the water is absorbed. 

REFERENCES

How to use an angle grinder to smooth concrete (n.d). The Tool Scout. Retrieved from https://thetoolscout.com/how-to-use-an-angle-grinder-to-smooth-concrete/

Berner, M. (n.d). How to level concrete slabs. Family Handyman. Retrieved from https://www.familyhandyman.com/list/how-to-level-concrete-slabs/

Worthington, T. (2007, September 25). Tools for the concrete pro: Angle grinders. Concrete construction. Retrieved from https://www.concreteconstruction.net/products/concrete-construction-equipment-tools/angle-grinders_o

Gibson, S. (n.d). What’s the difference: Abrasive cutoff wheels. Fine Homebuilding. Retrieved from https://www.finehomebuilding.com/2008/06/27/whats-the-difference-abrasive-cutoff-wheels

Tips for selecting the right diamond cup wheel. (2018, January 15). Gila Tools. Retrieved from: https://www.gilatools.com/blog/tips-for-selecting-the-right-diamond-cup-wheel/

Do you need to seal your concrete floor after grinding? (n.d). Barefoot Surfaces. Retrieved from https://barefootsurfaces.com/need-seal-concrete-floor-grinding/

Shelf life of grinding wheels. (2007, March 5). Norton Saint-Gobain. Retrieved from https://www.nortonabrasives.com/en-us/resources/expertise/shelf-life-grinding-wheels

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