Decorative concrete is a work of art, but it also has to be functional. That is why it is important for contractors to protect their work. And that is where sealers come in. The vast array of sealer products available on the market can often confuse a contractor who is looking for the right sealer for the job.
To help make that search easier, here's a breakdown of the general sealer categories, their characteristics and the situations each is best used in.
Sealers can be classified into two types: film-forming and penetrating. Film-forming, like its name suggests, creates a membrane - or film - on the surface of the concrete. These sealers do not react chemically with the concrete.
Film-forming sealers are often the better choice for decorative concrete because they provide a barrier of protection while highlighting the color and giving the concrete a finished look.
Penetrating sealers, unlike film-forming, do chemically react with the concrete. Instead of forming a protective layer on the surface of the concrete, these sealers penetrate into the concrete and act as a water repellent. They also give the concrete a dull, more natural looking appearance, says Bill John, manufacturing representative for sealer manufacturer TK Products in Minnesota. This type of sealer is generally used on non-decorative concrete.
Contractors can choose from several categories of penetrating and film-forming sealers. Since film-forming sealers are the more popular choice for decorative concrete, the following pages take a deeper look at the categories of film-forming sealers.
Acrylics are probably the most popular sealers, says Scott Thome, director of product services for L.M. Scofield. Acrylics are a breathable sealer, meaning they allow vapor to transmit out of the concrete through the sealer. These sealers can be used on both indoor and outdoor products and tend to come at a lower cost than most other sealers, Thome adds.
Acrylics are available in water-based or solvent-based forms. The water-based sealers have three parts: water, acrylic and a solvent. The acrylic component is what develops the actual film of the sealer. The solvent softens the discreet acrylic particles allowing them to fuse together and ultimately form a film. The water is the vehicle that holds the sealer particles. Once the water evaporates the remaining partilces then bond with the concrete and to each other, forming the sealer's film.
Solvent-based sealers, on the other hand, consist of just an acrylic and solvent. Solvents can be harder to use because the solvent evaporates so fast, Thome says. However, solvent-based acrylics are much less temperature and moisture sensitive compared to their water-based counterparts, he adds. That is why solvent-based acrylic sealers may be the better choice during the spring and fall seasons.
Contractors who use solvent-based acrylics also need to be aware of any environmental or VOC restrictions in the area in which they are working. These restrictions dictate the amount of solvent that can be used, and in some cases that results in some sealers being unusable in certain areas or on certain jobs, says Todd Asmuth, Surebond president. This is the case for all types of solvent-baed sealers.
As stated before, acrylic sealers can be used on both indoor and outdoor projects. However, Thome says that contractors working indoors, especially in occupied areas, should choose a water-based acrylic. "The water-based acrylics are much better for that because there's just a little bit of solvent in them," Thome says. Having less solvent makes these sealers safer for people exposed to the project and the sealer fumes.
If a contractor does use a solvent-based acrylic indoors, he or she needs to make sure the area is well ventilated.
When choosing between water-based and solvent-based acrylics, contractors also need to consider the effect the sealer will have on the color of the concrete. Most water-based sealers will not change the color of the concrete, John says. However, solvent-based sealers will darken the colors on the concrete. They can even darken plain concrete, John adds.