Preparing and Cleaning Concrete Surfaces for Coatings– Equipment Guide
If you are in the business of applying coatings to concrete which is a common need for contractors who apply epoxy coatings to floors or for contractors responsible for cleaning up graffiti or other surface contaminants, then you may wonder what options exist for preparing the surface. There are a variety of ways to prepare concrete and they each have advantages, drawbacks, and uses. In this article will cover the variety of options and there potential use.
Why Prepare Concrete
When cleaning a concrete surface your goal will usually be simply to remove any contaminant like graffiti from the surface. When prepping a concrete surface, you typically will be preparing the surface to apply a coating which will require removing any existing contaminants as well as creating a surface profile. The surface profile will maximize adhesion of the coating to the concrete surface which will improve the coatings performance.
Important Considerations for Only Cleaning a Concrete Surface
If you do not want to create a surface profile you will need to evaluate soda blasting as an option. Typically for cleaning a concrete surface without altering the surface at all using a soda sandblast is ideal. Soda blasters will remove any surface contaminant but will not alter the substrate of your product. Additionally, they can often be more effective at cleaning hard to remove contaminants from the surface. Soda blasters use baking soda which means that soda is left is not harmful to the environment, as long as the product that was removed from a surface had no harsh contaminants in it.
Alternatives to Soda Blasters for Concrete Cleaning
An alternative to blasting the surface for removing contaminants, is pressure washing. Pressure washing can also be effective at removing surface contaminants, it typically will not remove all contaminant from the product surface, unlike soda blasting which will usually result in a completely clean surface. Although it may not remove all contaminants, pressure washing will often be a necessary step even if you use a soda blaster as the power washer will remove any remaining blast media from the surface providing a cleaner substrate.
In addition to a pressure washer depending on the level of contamination, you can sometimes use chemical cleaners. There are a variety of companies that offer chemical cleaners for concrete. Before using chemical cleaners you will want to verify any potential concerns with disposal as well as the use of the chemicals. You will also want to verify if chemicals will be sufficient to properly remove the particular contaminant that is on your products surface.
Preparing concrete to apply a coating
if your primary goal is to apply coating to the concrete like an epoxy, you most likely need to create a surface profile. There are few options you can consider to create a profile in concrete, depending on the location and size of concrete you will be preparing.
One option is a diamond grinder. A diamond grinder will remove existing coatings and create a surface profile as well. Diamond grinding will also often create a smoother profile then the other options. It is well suited for horizontal surfaces as well as for cleaning up a surface that too rough of a profile has been created. It can usually achieve a surface profile of CSP 2 – CSP 3 which is useful for applying seamless coatings or roll on/ spray epoxies.
A second option is shot blasting. Shot blasting is a form of sandblasting that uses steel shot to create a surface profile. A Shot blasting machine to prepare concrete has an enclosed chamber that propels shot at the surface and then reclaims the shot to reuse it. Shot blast machine units can be used to remove polyurethane coatings that are up to 10 mill stick as well as other heavy coatings including mastic’s. They can also be used to create a surface profile. With heavier coatings, you may need to perform multiple passes to properly prepare the surface. Shot blasting is a relatively dust free operation compared to the other methods mentioned. Shot blasting machines work well with horizontal concrete surfaces. Shot blasting can create profiles anywhere between CSP 3 – CSP 7 making it one of the most versatile in preparation options. It can be used with coatings from seamless coatings to cement screeds and trowel on epoxies.
A third option, is scarification. Scarifiers remove coatings up to a quarter inch thick and can also be used to create a surface profile. They typically can create the deepest profiles of the three options. Scarifiers are also ideally suited for horizontal surfaces. They create profiles from CSP 6 – CSP 9 which is well suited for heavy coatings like cement screeds.
A fourth option for a lighter profile is acid etching. Acid etching uses acid to properly create a profile. The challenges with acid etching include safety with the chemicals used as well as limitations in what they will remove from the concrete surface. They are limited to CSP 1 level profiles.
A fifth option that is ideal for vertical surfaces is a sandblast pot. To create a profile on concrete, you’ll want to consider a blast media like crushed glass or coal slag. Crushed glass or coal slag can provide a mill profile between 2 to 6 depending on the size of the media use. To learn more about crushed class versus coal slag you can review this article. In addition to the media you will want to use the correct blast pressure to ensure you achieve the profile you want. A blast pot will also not contain the blast media typically and so you will want to protect any surfaces that you do not want coming in contact with the blast media.
Other Concrete Preparation Options for Small Areas
In addition to the options listed above for prepping larger surfaces of concrete there are hand tool options for prepping small areas of concrete. Common options for prepping smaller areas of concrete or areas of concrete by hand include needlers along with handheld scarifiers, and scabblers. Needlers are ideal for texturing concrete. Scarifiers are well suited for heavy coating removal and surface preparation (see above). Scabblers are well suited for roughening and leveling concrete surfaces they create a rougher surface typically than the other two methods.
Conclusion
By evaluating whether you are blasting a horizontal or vertical surface as well as the profile goal that you need, you can better decide which equipment application is best suited for your particular needs.