Polyaspartic polyurea coatings have been on the market for more than a decade. Their advantages are many: ultra-fast installation, no UV fading, able to be applied at a wide variety of temperatures, resistant to high in-service temperatures, and highly abrasion resistant. They’re expensive, though, and best suited for smaller projects that demand a very fast turnaround, like garage floors and countertops. They’re also susceptible to contaminants and moisture in the concrete, which can cause delamination.
To get it right, start by asking the manufacturer of the product you’ll be using to train you.
"It's not that installation is difficult, it's just that we want people to employ a repeated process,” says Flexmar Polyaspartics president Jack Bracco. “Installers who’ve been using epoxy or polyurethane have their own way of doing things. We’re trying to standardize the process to ensure success."
And, as always, follow the manufacturer’s instructions.
Step 1: prepare the surface
As with any coating or topping, surface preparation is critical and the first step. Ridding the surface of laitance and contaminants is critical. The polyaspartic is a very low-viscosity material, and it must be able to penetrate the surface.
Acid etching adds moisture to the concrete and the lower pH can lead to delamination problems. Dry diamond grinding is preferable, although shot blasting may also be used. Most manufacturers recommend a diamond grind at a 60 grit to 80 grit -- just enough to get through the paste surface layer and open the concrete’s pores. Others start with a higher grit count—up to 1800. The floor should end up with a surface profile of CSP 2 to CSP 4, depending on manufacturer. Finally, thoroughly vacuum to get a dust-free surface.
A significant concern for polyaspartic coatings is contaminants in the concrete. “Oil, grease, or other chemicals will almost certainly lead to future bonding issues and should be appropriately dealt with,” instructs global manufacturer HP Spartacote. “Biodegradable degreasing agents as well as organic oil emulsifiers work well to help clean contaminated areas.”
Step 2: test moisture level
New concrete floors should dry for at least 28 days; 60 days or 90 days is preferable. Ideally, because high moisture can debond the coating, there should be a vapor retarder beneath the slab.
Test the floor for internal relative humidity (RH) using ASTM F2170 or moisture vapor emission rate (MVER) using ASTM F1869. (Internal RH is more revealing.) Manufacturers typically recommend moisture levels no higher than 75% internal RH or MVER readings of 3 to 3.5 pounds/1,000 square feet. If levels are higher than recommended, use a moisture mitigation system. Bracco, however, says that the polyaspartic penetrates into the concrete pores and the moisture acts as a catalyst resulting in a bond strength that is higher than the tensile strength of the concrete. Some installers, though, insist on an initial epoxy primer coat.
Step 3: repair surface defects
Flexmar’s Bracco recommends filling cracks with sand and then wetting the sand with polyurea. This approach cures in about 20 minutes, and the joint can then be ground flush with the concrete surface. Polyaspartic coatings have such great elongation properties that you can simply install the coating right over the top of these repaired cracks without getting any reflection, although this does not include contraction joints—finish up to and into the joint but not across the top. Most contractors won’t fill and cover a joint since that can easily result in a crack at mid-panel.
Step 4: mix and prime
Polyaspartics are a two-part system usually mixed with equal amounts of Part A and Part B. The resulting material is virtually odorless and has very low viscosity—almost like water. The primer coat and bed coat typically contain pigment. If using a pigment, add it to Part A. Then use a notched squeegee and backroll the recommended number of coats, staring with a self-priming coat of polyaspartic. Use a brush to cut in at the edges.
The self-priming coat is when you can see whether the material is wetting: absorbing into the concrete. Different manufacturers recommend different thicknesses for the primer coat, ranging from 2 mils to 3 mils up to 10 mils to 15 mils.
"Bonding comes from two things: surface profile and the ability to flow into the substrate," says Bracco. “With polyaspartics we have a little extra time before it cross links, so it has time to absorb into the concrete."
Step 5: apply subsequent coat/s
Within an hour (or less, depending on temperature and humidity) the primer coat will have cured enough to walk on. For applications that incorporate vinyl chips or quartz sand, the second coat (or bed coat or build coat) is put down. For applications with color, both of these first two coats incorporate pigment. For floors with vinyl chips or decorative quartz, that material is immediately broadcast into this "bed" layer while it’s still wet to refusal. Use spiked shoes to walk on the wet surface. This layer varies from 2 mils to 18 mils thick, with the vinyl chips adding as much as 8 mils. Metallic effects can also be added to the build coat.
"The chips wet out to form a laminar layer parallel to the floor," says Bracco. "The ability to wet those chips is very important. Epoxy has a much higher viscosity, so the chips tend to lay on edge. Polyaspartics wet out the chips and they lay down to give you the laminar effect that helps in the overall protection of the concrete."
Step 6: apply top coat and clean up
For decorative quartz or vinyl chips, scrape the surface with a floor scraper and vacuum up the loose chips. That makes it smoother and reduces the amount of product needed in the top coat to cover the vinyl chips. Pour a ribbon of the polyaspartic near the edges (use a plastic garden watering can with the spout removed) and cut in with a brush. Pour ribbons onto the floor and roll out the top coat. The top coat is always clear and goes on at 6 mils to 18 mils. Thinner coats are applied with 3/8-inch nap rollers and thicker coats with ¾-inch naps. Thinner coats leave a slight texture to the surface because some of the vinyl chips or quartz pokes through.
Final coating thickness ranges from 11 mils to 40 mils. All this can be accomplished in one day. Typically, the floor can be opened to foot traffic in five hours for a three-coat system and driven on within 24 hours.
This system produces a beautiful floor in only a few hours. Why then aren’t polyaspartic coatings more popular. Some have reservations, like epoxy expert Jack Josephson, owner of Real World Epoxies. “I found the working time was too sensitive to relative humidity. At 50% RH it was nice and workable but at 65% it would speed up too much and I couldn’t keep a wet edge. Also, I found that adhesion to itself outside of a recoat window was a potential problem.”
Mike Meursing with Garage Coatings.com, explained his concern that “Bayer always recommended an epoxy primer under the polyaspartics. So, we offer a fast-drying epoxy primer and a polyaspartic topcoat which provided the maximum benefits of each product.”