How to Concrete Grinding [3 Methods,11 Steps & Cost Overview]
As the name suggests, concrete grinding is a process of improving the surface texture of concrete using concrete grinders.It’s a process very similar to sanding wood. The concrete grinders are fixed will diamond-segmented blades (like sandpapers).
They are used to grind down the concrete surface to achieve the desired degree of smoothness and shiny texture in the concrete.
Like the process of sanding wood, when the grinder moves on the concrete surface, it produces fine particles of concrete dust due to grinding.
After removing the concrete dust, a fine mirror-like glossy finish is obtained.
Concrete can be grinded using a grinder either following the dry or wet method.
Dry grinding of concrete
In case of dry grinding of the concrete, the concrete grinder with different types of abrasive disk blade (most commonly diamond) is rubbed over the concrete surface
Initially, a coarse texture is obtained but with time a finer surface with a shine is obtained.
During the grinding process, much of the dust is vacuumed up. Though some dust also goes into the air. Which is not only harmful to the worker but also the environment.
Some of the advantages of dry grinding methods are following:
- A more shiny surface is obtained.
- It can also harden and condense the slab.
- It can be applied both to open areas and closed corners due to the high mobility of the grinding machine.
Wet grinding concrete
In the case of wet grinding of the concrete, water is used to capture the dust. As a result, a slurry of concrete is formed at the end of this process.
Due to slurry formation, there is no dust in the air and hence we have reduced air pollution. A similar type of griding disks is used as in the dry grinding of the concrete.
However, the final look of the concrete has a low luster rather than the glossy one.
The wet slurry is sometimes is also a problem as it may be difficult to clean the surface. You may also face problems with its proper disposal.
Some of the advantages of wet grinding methods are following:
- It has shorter downtime.
- This technique is less costly.
- We can also make use of propane-fueled machines as they are more environmentally friendly.
- It is a dust-free process and there is dust contamination.
Hand grinding methods
This technique is perfect for grinding a shelf or a countertop. Usually, the hand sanding technique uses sandpaper or a hand grinder, or a random orbital sander.
It may take some time and effort as labor has to work with hand. But it gives the desired results with the greatest amount of satisfaction.
Polishing Concrete Floor(Setp By Step)
Following steps should be followed while polishing the concrete.
- The first step is to remove the existing concrete coating. For coatings of very high thickness, you may use a 16 or 20 grit diamond abrasive blade or may also opt for a more aggressive tool specifically for coating removal, such as a T-RexTM.
- The next step is to seal the cracks and joints with epoxy or other types of semi-rigid filler. Remember, this may also add up the cost.
- The previous two steps were the pre-polishing and grinding steps. Now, the next step is to grind the floor with a 30 or 40 grit metal bonded diamond blade.
- After that keep on increasing the grit size of the metal-bonded diamond and keep on grinding.
- Now increase to a 150-grit metal-bonded diamond. This size of grit can be used if a finer look is desired.
- After grinding with the 150-grit diamond, you must apply a chemical hardener to densify the concrete surface.
- Now you can start the polishing. Start with a 100- or 200-grit resin-bond diamond, or a combination of the two.
- After that, polish with a 400-grit resin-bond diamond.
- Then you may proceed to also polish with an 800-grit resin-bond diamond.
- Lastly, 1500 or 3000 grit resin bond diamond may also be used depending on the desired level of shine you want to achieve.
- As an option or an extra, you may also protect the polished surface using a stain guard. This will also make it easier to maintain the surface.
The Time Required For Grinding
Depending on the area and amount of polishing required, it may take 2 or 3 days to finish the job. However, once the floor has been polished it can be used immediately.
Cost of Concrete Grinding
Concrete grinding cost depends on the area you are working on and the geographical location of course.
Usually, it may cost you around 3$ to 12$ per square foot to polish concrete. Usually, the cost of dry grinding of concrete is more expensive.
On the other hand, wet grinding of concrete is cheaper. Concrete grinding costs depend on several factors.
Shape and size
The larger the floor is the lower will be the per square foot cost of grinding the concrete. For example, per square foot cost of concrete grinding for a small house floor may be much higher than the floor of a large commercial building.
The is simply due to the bulk discount. Certainly, more cost will be incurred for surface areas that may have angles and curves.
If the floor you are grinding is with a large number of obstacles, then it may cost you more to polish. For example, if a concrete floor has obstacles like multiple doors, cabinets, stairs, or other hindrances, it would be difficult for worker and the machine to work around them.
Amount of grinding
The amount of grinding you desire certainly will affect the cost per square ft. The amount of shine equates to the time labor must rollover the machine on a concrete surface to obtain the desired glossy look.
For a high amount of shine in concrete, the labor would have to roll over the machine on concrete multiple times, which will certainly add up the cost.
If the surface of the concrete is not ready for grinding, it must be prepared first. This will certainly add up the costs. For example, if the concrete surface is cracked, you may have to first fill up the crack and then polish it.
Similarly, if there are some serious damages to the concrete you are about to polish, you may have to repair it. That will certainly raise the cost.
For existing concrete, sometimes a color of epoxy coating are present. In such cases, they must also be removed to proceed with grinding, which obviously will add up the per square foot cost.
To conclude, in this article we discussed different grinding techniques, what are the advantages and disadvantages of certain techniques. A detailed step-by-step process of grinding is also explained with indications on the type of blade disk to be used. The grinding jobs may require 2 or 3 days to complete depending on the area and complexity of the job.
Lastly, the hint of the cost of polishing concrete is also provided with explanations on the factors that can cause the costs to hike up.