Is Your Concrete Ready to be Coated?
by Carlos Santana - Sales Representative - Arizona, New Mexico and Nevada
How to determine if it’s the right time to apply a standard thin film floor coating
You may have been in this situation: the client is anxious, the installation team is on standby and there’s building pressure to meet a tight timeline. However, you’re unsure if the concrete itself is ready to be coated.
Prematurely applying a coating – no matter how smooth an installation may be – is likely to result in a flooring failure, whether you’re working on an industrial flooring project, or residential. To avoid costly and time-intensive reinstallations, we recommend you closely evaluate the condition of the concrete before applying a standard thin film floor coating. Consider the following:
Moisture: Has the concrete reached its full 28 to 30-day cure? Watch for dark spots and efflorescence, as this could be an indicator of moisture wicking up through the concrete from underneath the slab. (Learn more about Testing for Concrete Moisture.)
Hard Power Troweled Concrete: Concrete can appear blackened or burnt following a tight finishing with a walking trowel, or if it’s burnished using a walk-behind power trowel. In this case, you must grind or shotblast the concrete to get past the top layer, or cream of the concrete, to create the proper profile for long-term adhesion. Fiber-filled concrete will be a challenge, as the fibers will need to be burned using a propane weed burner prior to applying a primer.
Silicone Oils and other Contaminates: Armor All products and other types of tire dressing will act as bond breakers. The easiest way to determine if the concrete has these types of contaminates is to saturate the concrete with water. The concrete will immediately, or at least within a minute, darken as the water absorbs in areas with no contaminants. You would immediately notice whitening or a frosty hue in areas that have silicone-type contaminates. Further, check to see if the water beads up and then takes more than a couple of minutes to absorb. If so, there is either some sort of sealer, curing compound or other form of contaminate in the concrete that must be removed prior to coating installation.
Laitance: Laitance is the very brittle and weaker layer of cementitious material of the concrete. It looks like a dust residue and has multiple fine cracks that appear to have a shattered or crazed look to it. This is created during the hardening process from:
- Over manipulating the concrete during concrete placement
- Too high of a water-to-cement ratio from the mix design
- Spraying additional water to the surface in order to finish and smooth out the concrete
- Concrete may have gone through a freeze thaw cycle during the curing process.
- In each case, the concrete has ultimately become so fragile that you can carve into it with very little effort.
If you encounter laitance, you will need to grind or possibly shot blast past it. Once complete, scrape the surface with a screw driver or drywall screw to ensure all excess laitance has been removed. You can also use a specificity tool to test hardness, such as the MOHS Hardness Test Kit. Since laitance is another form of a contaminant, you may need to use densifiers to harden the surface.
It’s important to remember that each installation is unique. In some cases, you may be able to use specialized products and systems that can overcome some of these installation challenges. For example, when dealing with excessive moisture, our VaporSolve line of products and systems can help. They are designed to withstand all levels of excessive moisture, including concrete with high levels of efflorescence. If you have questions about application techniques, reach out to your technical representative.
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