As a porous material, unsealed concrete is prone to cracking and staining. It is also vulnerable to penetration by a host of substances including oils and solvents. When sealing concrete, it’s important to match the sealer to the concrete and take into consideration how and where the concrete will be used.
Selecting the Right Sealer
The right sealer for any given concrete surface depends on where it will be used and the conditions it will face. An interior surface, like a garage or basement, may benefit from a different sealer than an outdoor application like a driveway. Before selecting a sealer, a homeowner should have an idea as to the desired outcome and type of finished surface—glossy or low luster, slippery or rough. Finally, concrete surfaces respond to a number of factors, including regional climate.
Film-forming and penetrating sealers are the two main types of concrete sealers available. Film-formers are applied to the surface of the concrete and protect it by forming a surface layer or lightly penetrating the top of the concrete. Film-formers are often acrylic products that add a gloss or sheen to the surface, highlighting the colors, stamping, or aggregates in the concrete. Film-forming sealers are meant to be reapplied once every one to four years, depending on the manufacturer’s directions. Film-formers can make the surface slick and are sometimes prone to peeling. Proper reapplication is important—simply applying a second coat to a failing first coat will lead to poor results. Film-formers can be great solutions for interior application, where resistance to stains, scuffs, and scratches is important.
Penetrating sealers—also called "penetrants," "reactive" or "internal" sealers—migrate below the surface and undergo a chemical reaction with the concrete to bond and fill the voids between the particles. A penetrating sealer travels anywhere from 1-4 ml below the surface to interact with the lime in the concrete, forming a glass-like substance that protects against moisture intrusion. Penetrating sealers are most commonly silicates, silenes, and siliconates. A penetrating sealer tends to protect concrete longer than film-forming sealers, but they can also leave the surface prone to staining. Penetrating sealers can offer great protection in regions that are prone to freeze/thaw cycles.
Preparation and Maintenance
Regardless of the sealer, most manufacturers insist that the concrete surface be cleaned prior to application. As a general rule, homeowners should use a hot-water power wash, and a concrete-specific detergent with an alkaline pH. "Homeowners should scrub the surface, let it set, power-wash it, and then rinse," says Jay Tarantino, senior tech support advisor for The TARA Distribution Group / V-SEAL, an international manufacturer and distributor of concrete sealers. Tarantino advises homeowners to take special care with newer concrete, as improper cleaning could weaken the still-sensitive substance.
Homeowners should expect to maintain a sealed concrete surface. This includes regular cleaning and immediate attention to spills. "Understand that some stains are permanent," Tarantino says. "You can’t get everything out of concrete. But you should respond and attend to spills ASAP." Manufacturers’ recommendations should be followed for cleaning and maintenance.
Beware of Sealer Claims
The concrete sealer market is filled with manufacturers’ guarantees and "magic bullet" solutions. "There is no solve-all product," says Grant Loyd, founder of Solving Concrete Problems, an online concrete sealer store and contractor network. "Everything is going to have pros and cons, but advertising won’t tell you that." Loyd advises homeowners to first look at the problems they are trying to avoid or remediate, and then shop accordingly. Tarantino suggests products that pass ASTM testing, including ASTM 309, 1315, 90-day ponding, and 100-day freeze-thaw tests.
Experts also agree that a concrete sealer will only perform as well as the substrate itself. If a homeowner is having a new surface poured, he or she should insist on a water-cured product. This technique is becoming less common in the concrete industry, as it requires frequent visits from the contractor while the concrete cures. "Water-cured concrete performs 50 percent better than concrete that isn’t water-cured," says Loyd. Although water-curing a concrete surface may cost more, it is a smart investment. Similarly, homeowners should not skimp on concrete sealer. "You get what you pay for," Loyd says.
Credit: Renovate with Tommy Mac