If a contractor uses a solvent-based sealer it is important the customer is aware that the color will change. This could be a determining factor in the choice of water-based versus solvent-based.
Epoxies are a much less permeable sealer. Unlike acrylics, an epoxy will not permit the concrete to emit vapor through the sealer. This is an important consideration when choosing to use an epoxy.
"If the concrete wants to breathe and give off vapor the epoxy will trap it in the concrete. That alone says do not use epoxy on an exterior in a freeze/thaw environment," Thome says. In a freeze/thaw environment, the moisture trapped in concrete can freeze and put stress on the internal parts of the concrete causing it to break from within, he explains.
Epoxies are also not UV stable, so if they are placed outdoors or in an area where they are exposed to UV rays the sealer will yellow or chalk, John says.
Like solvent-based acrylics, epoxy sealers will darken the color of the concrete.
Epoxies are a great choice for indoor projects, Thome says. They are a common sealer choice for garage and basement floors. They offer a durable, abrasion-resistant surface. Additives can also be added to the epoxy to create a slip-resistant material.
Epoxies are available as water-based, solvent-based or 100 percent solids. Water- and solvent-based epoxies tend to be more user-friendly because they have a longer pot life than the 100 percent solids epoxies. "If you're a novice and somebody just asks for a gray epoxy floor in their garage I would suggest solvents or water-based epoxies," John says.
The 100 percent solids epoxy is a more durable, chemical-resistant sealer, John says. Both the 100 percent solids and water-based epoxies have little to no smell so they can be used in enclosed areas. Solvent-based epoxies can be used indoors, but the area needs to be well ventilated.
When it comes to applying an epoxy sealer, preparation is a huge factor, John says. "How you prep could determine what product you use to make the floor look smoother, rougher, or whatever the case may be," he continues.
For example, if a contractor preps by shot blasting he removes part of the surface. "This leaves normally a 15-mil profile in the concrete. In order to cover up that profile you need to use a
100 percent solids," John says. Other prepping techniques may keep the concrete smooth enough that a 100 percent solids epoxy will not be required to cover up any profile or roughness.
Epoxy Modified Polymers
This type of sealer is a water-based, low VOC sealer that is a blend of acrylic and epoxy. "They combine the strength of an epoxy with the flexibility and breathability of an acrylic," Asmuth says¬¬¬.
This type of sealer can be a good choice for projects that have low VOC requirements or a project that is looking to earn LEED (Leadership in Energy and Environmental Design) points. It is also UV stable, Asmuth says. The combination of low VOCs and UV stability makes it a good sealer for both indoor and outdoor projects.
Epoxy modified polymers can be used on green concrete because it allows moisture to leave the concrete while not interfering with set-up. Having the ability to seal before the concrete has completely cured saves time on a job and also allows pedestrian or building traffic back onto the concrete quicker because the contractor doesn't have to wait until the concrete is fully cured to seal.
Like an epoxy, a urethane is a durable, abrasion-resistant sealer. However, it is more flexible than an epoxy, Thome says. Urethanes can be used over epoxies to give the concrete and the epoxy sealer extra protection, he adds.
However, urethane sealers can be used on their own as well. "It is a longer life product - better wear, better gloss in most cases," John says.
Urethanes come in both water- and solvent-based versions and work best on interior surfaces. "Urethanes are probably the most problematic because they can be very humidity and temperature sensitive even in buildings," Thome says. "A contractor has to be aware of the entire environment. Not only what is above the concrete but what is in the concrete as well."