Concrete sealer

Concrete sealers are applied to concrete to protect it from surface damage, corrosion, and staining. They either block the pores in the concrete to reduce absorption of water and salts or form an impermeable layer which prevents such materials from passing.

Research from major concrete authorities, including American Concrete Institute, Portland Cement Association, and National Ready Mix Concrete Association; confirm that most concrete damage is attributable to surface moisture intrusion. The most pervasive form of concrete damage is surface scaling from freeze/thaw. Other forms of damage include alkali-silica reaction (ASR), chemical intrusion, and corrosion of steel reinforcements.

In past decades attempts to protect concrete have included sealers ranging from wax to linseed oil. Today, high quality concrete sealers can block up to 99% of surface moisture. There are two main sealer categories: topical sealers (coatings) and penetrating sealers (reactive).

Topical Sealers: Topical Sealers can provide visual enhancement as well as topical protection from stains and chemicals. They require a dry, clean surface during application to gain adhesion. Topical sealers may alter the coefficient of friction which can make substrates slick when wet – a condition that can be remedied by adding anti-skid materials. Life span is generally 1-5 years, although high-end epoxy/urethane systems can last significantly longer.

Penetrating Sealers: Penetrating sealers can be applied to dry or damp surfaces and should be properly matched with substrate porosity in order to effectively penetrate the surface and react. The chemical reaction bonds active ingredients within the substrate blocking surface moisture. Penetrating sealers generally do not significantly modify substrate appearance or traction. Lifespan is generally 5 years or more.

Acrylic Resins: Acrylic resins form a topical film membrane on the substrate surface. They are available in both water-based and solvent-based formulas, affordable, and generally simple to apply. They are well known to increase perceived visual enhancement (sometimes described as a “wet look”) and can provide good UV protection for colored substrates. Despite being the softest and least lasting of the major sealer categories, price and convenience make acrylic resins a very popular choice for decorative concrete such as stamped concrete and exposed aggregate. Acrylic resins are also commonly used as curing agents for new concrete, and many comply with ASTM C309.

Epoxy/Urethane Systems: Epoxy/urethane systems are also topical film membranes. They share many of the same characteristics as acrylics, but the performance levels and life span are superior and commensurately more costly with more complex installation requirements. Novolac epoxies are particularly noted for chemical resistance and acid resistance. High-end urethanes are known to be extremely abrasion resistant. Epoxy/urethane systems are frequently used in demanding applications such as factory floors, garage floors, and restaurants, and water-based versions are often used to seal concrete countertops. Epoxy/urethane systems are generally applied only to fully cured existing concrete, although certain epoxy products can comply with ASTM C309.

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