Surface Prep to Restore an Old Concrete Floor

Surface prep to restore an old concrete floor removes old material and prepares the substrate to receive the new coating. This is a key part of how to restore an old concrete floor. Resurfacing old concrete is a cost-effective way to get more life out of the floor, but the surface must be properly prepared to accept the new coating.

Typically, old concrete floors have been covered with tile, carpet, paint or epoxy. This means the surface is likely covered with glue, paint, and/or leveling compound, which all needs to be removed. If the material and old adhesive are not removed properly, the new overlay will not properly adhere to the floor. 

Determine the right grinder for the job.

The first important part of surface prep to restore an old concrete floor is to remove the old material and level the surface of the concrete. Concrete grinders are used for this because the grinders are heavy, to make contact with the concrete, and the grinding wheel is a serious chunk of metal that will take the top layer of concrete off. The heavier the grinder, the more contact the grinding wheels will make with the concrete, and the faster the work can be completed. 

Choosing the right grinder is a key part of this. A too-small grinder will be ineffective and will take longer to grind off what is necessary to remove. The power source must be considered. Grinding machines come in 115-volt single-phase, 220-volt single-phase, 240-volt three-phase and 480-volt three-phase power. Single-phase machines can be powered by typical electrical outlets which are found in most residential and commercial buildings in the United States. The more powerful machines need a different source of electrical power, such as a generator.

Understanding diamond tooling.

Concrete grinding relies on diamonds on the grinding discs. Diamonds are the hardest material that is used to wear away the material they are grinding against. The way that diamond tooling is rated can seem counter-intuitive, but once you understand the system, it will be easier to pick the right diamond tooling or the job. 

The bond of a diamond tooling is what the material, or matrix, the diamond chips are embedded in is called. The matrix can be metal or resin. The matrix holds the diamonds in place so they are exposed to do the grinding. During grinding, the matrix gradually wears away to expose new diamonds. On hard concrete, a soft-bonded diamond needs to be used, so that more of the matrix wears away to expose more diamonds as work progresses. On soft concrete a hard-bonded diamond needs to be used, so that less of the matrix wears away to expose less of the hard diamond-grinding surface.

Get your vacuum system in place.

Concrete grinding creates a lot of concrete dust. Concrete dust is unsafe to breathe in and can cover anything that is in the room. The room will need to be emptied and anything that is in the room, such as appliances or built-in furniture, will need to be protected with plastic sheeting. 

Watch here the surface preparation process – https://www.duraamen.com/video-gallery/concrete-surface-preparation

How will you grind?

The old surface material can be removed in two ways. Grinding is done using a dry or wet grinding method. The process of grinding creates a lot of heat from friction. Wet grinding uses water to keep down dust and cool the grinding surfaces. Some dry grinding wheels have been specially formulated to withstand the friction from grinding without the need to use water. While the end result will be the same for wet or dry grinding regardless of what method is used, there are some differences. 

• Dry grinding

  Dry grinding takes longer. The right bond here is of extra importance, so that the diamonds wear away in even amounts. Softer bonds are used in dry grinding.

• Wet grinding

  Wet grinding can be completed faster. As the concrete dust gets released, the water meets with the dust to form an abrasive slurry. The grinding pads will wear out faster due to this abrasive liquid bathing the work surface. Wet grinding typically creates deeper scratches on the concrete from the diamonds. Cleanup is more time consuming with wet grinding because of the water, which must also be safely exposed of. 

Start large and work down.

Whichever method you choose for your surface prep to restore an old concrete floor, remember that grinding is a process. You do not start with the finest grinding pad and use that the whole time. Start with a course grit to make large scratches and surface removal and then gradually work down to a finer grit for smoothness and polishing. The large grit will make large-scale scratches, while the finer grits will create many fine, smooth scratches that are close together. This is what you want to achieve for the best surface prep on your floor.

Once you have removed the old surface material and you have a network of fine scratches all over the surface of the concrete, that concrete is ready for polishing or for an overlay. This focus on surface prep will give your restored concrete floor the best chance for success. 

Surface prep to restore an old concrete floor is the first part of the job but is perhaps the most important, as this step is what prepares the concrete to receive the new flooring system.

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