Concrete Scarifier vs. Grinder: Which is Right for Your Project?

With all projects, selecting the most efficient piece of equipment to perform the work increases not only production but also provides a safe work environment for you, your employees, and others in the work area.

When selecting a method of surface prep, having a goal will guide you through the selection process. The amount of concrete to be removed, and the roughness (concrete surface profile – CSP) needs to be decided.

This article will go through the basics of concrete scarifiers and grinders. There are multiple manufacturers of each type of equipment. It is not the intent of this article to compare them all. It will be comparing what the capabilities of a concrete scarifier and grinder are.

Understanding Concrete Scarifiers

A concrete scarifier is for removing stock. The primary features allow you to adjust the depth of cut, speed of the machine, and concrete surface profile obtained. All these features are important when selecting this method.

A concrete scarifier (milling machine) is a drum type machine. The drum spins at a high rate of speed on a horizontal plane. On the drum there are different configurations of wheels or flails. The aggressiveness and configuration of flails used is based on what your intensions are. The amount of removal and roughness of the cut will direct you to the proper set.

The concrete scarifier is best at removing stock. When there is curling at a joint, one side higher than the other, and the goal is to have both shoulders of the joint on a level plane, a scarifier will do the job. If there is a high spot somewhere in the floor that needs leveling to the same height as the surrounding area, a scarifier will be the machine of choice. Depending on the flooring system, a scarifier might also provide the ultimate surface profile.

Other uses for a scarifier include:

• Concrete and asphalt removal
• Surface recycling
• Pavement marking removal.
• Floor preparation or cleaning
• Increasing the slip resistance of a surface

Understanding Concrete Grinders

Although a concrete grinder will remove the concrete surface, it has its limitations on the depth it can remove. Using diamond abrasive tooling, the grinders head turns and rotates on a horizontal plane. The head could be anywhere from 16” – 36” in diameter. It covers a larger area than a scarifier, which can be good and not so ideal.

Imagine a flat, twenty” rotating plate fitted with diamond tooling removing an 8” wide concrete joint lip that is raised 1.00”. You will need to run up and down the joint multiple times to remove the lip. A grinder cannot remove the amount of stock as a scarifier and works best when all the tooling is in contact with the concrete surface.

Grinders perform best when removing a coating, preparing the substrate for a surface applied system, or to perform the polishing process. With all the available tooling, the grinder’s versatility increases tremendously. Tooling ranges from an ultra-fine three thousand grit abrasive for developing a high polished shine and as aggressive as a bush hammer that produces a very rough surface profile, ideal when installing a cement-based overlay.

It is difficult to remove a predetermined amount of the surface when using a grinder. It is very indiscriminate. There is no way to mechanically adjust the cutting depth. A concrete surface is not completely flat. No matter how large or small, there are hills and valleys throughout the slab. When a grinder passes over these hills, it will remove them to the level of the valleys. Once the floor is flat under the grinding plate, it will then grind uniformly.

The choice of diamond tooling used will provide the speed and surface profile the grinder obtains. If speed is a concern, you can use a coarse diamond tool. This will be the most efficient way to remove stock. The amount removed will be based on the strength of the surface, weight of the grinder and the number of passes made over the area. When removing ¼” or greater, multiple passes will be needed and that will drive up the removal cost.

Grinders are best when used to prepare the surface to accept a coating or when polishing. It can roughen the surface when applying a coating system or produce a highly polished concrete surface.

Concrete Scarifier vs. Grinder: Key Differences

• Scope of Work: The goal is to remove ½” of a concrete surface over a one hundred sq.ft. area.
• o Using a scarifier will be the most efficient method. It might take two passes with each pass removing ¼.” The surface profile will be rough. If applying an overlay or just to increase the slip resistance, the surface profile will be perfect.
• o“Bush hammer” tooling will be needed initially if trying to perform this work with a grinder. Bush Hammers will remove stock, but it will be difficult to dial in the depth of removal. The depth will be random, and difficult to control.
• Scope of work: The goal is to remove an ¼” of concrete on one side of a raised control joint shoulder leaving a smooth surface for easy wheel transition over the joint.
• oUsing a grinder and proper tooling, continually make passes down the joint while grinding only the high side. Repeat until the raised lip is at the same level as the adjoining side. The surface will need no added processing after they are of equal height.
• oA scarifier can be used to lower the high side. Once completed, the rough surface will need to be ground smooth with a grinder. The scarifier will leave the surface very rough. At this point, the surface profile will not meet the scope of work. Using a grinder, the roughness needs to be reduced.

As you can see, using the correct method will increase efficiency.

Choosing the Right Tool for Your Project

When evaluating methods to perform the task at hand, there are factors that need to be addressed. If heavy stock removal needs to be done, a scarifier needs to be the first method on the list. A scarifier can remove concrete with great efficiency. Once the depth is set on the machine, it will remove concrete at the same depth throughout the entire area.

If preparing the concrete substrate for a coating or overlay, a grinder will perform the work very well. The tooling used will produce the surface profile. They range from very rough to a highly polished surface. This cannot be performed with a scarifier. If minor surface imperfections need to be addressed, a coarse diamond tool on a grinder will do the trick.

Conclusion

Both methods have their own strengths. Whether it be speed, depth of cut, or the intended final surface profile, one of the two or both methods used in conjunction with each other will perform the work.

To remove stock, a scarifier should be used. This will be the most efficient method. If a long, narrow area needs to be addressed such as removing lines on pavement, a scarifier is easy to adjust for this purpose. When preparing a slab for a coating or overlay, a grinder is an excellent choice. With the wide array of tooling available, one can certainly be selected based on the needed profile.

No matter what your project entails, Niagara Machinehas the equipment to perform the work. Scarifiers and grinders are their specialty. No matter what the project size is, they have one available that will suit your needs. If purchasing does not fit in with your plan, renting from Niagara’s rental partner, Sunbelt Rentals, is always an excellent choice. They have both options available to get your project on track and successfully completed.