What are Concrete Sealers?
Concrete sealers improve the durability, stain-resistance and appearance of concrete floors, structures and driveways. Sealers are either of the penetrating or film type:
Penetrating Sealers
React chemically to penetrate the concretes pours and protect the concrete against water, ice and de-icing chemicals. They act invisibly to protect exterior concrete from freeze-thaw damage and from corrosion. The better products allow water vapor to escape the concrete. Penetrating sealers often contain compounds such as:
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- Silane – a small inorganic compound of formula SiH4 that clots concrete pores via covalent bonds. Silane resists water and oily stains, has low viscosity and is often used to seal dense concrete that has fully cured.
- Silicates — an oxide containing silicon and a cation such as lithium or sodium. In contact with concrete, silicates form calcium silicon hydrate, which adds density and can be polished to a high sheen.
- Siliconates — compounds such as K4SiO4 (potassium methyl siliconate) are extremely hydrophobic and protect concrete from freeze-thaw water damage.
- Siloxanes — large molecules in which an oxygen atom attaches to two silicon atoms. Siloxane-based sealers are useful for protecting exterior concrete and porous concrete block.
Acrylic Resins
Acrylic resins form a protective film on concrete in both interior and exterior applications. These can be water- or solvent-based. They quickly dry to various glosses and enhance the beauty of stamped, colored or decorated concrete. They provide good protection against water and salts, but require regular maintenance with a floor wax or finish.
Polyurethanes
Polyurethanes build a thick protective film that helps protect high-traffic areas. They resist wear, chemicals, scuffs and stains while imparting a matte or gloss look. The finish won’t yellow and is transparent. Care must be taken to protect polyurethanes from water until they finish curing.
Epoxies
Epoxies are usually two-component mixtures. They form a tough, thick glossy film that is often used to seal concrete countertops as well as high-traffic floors. Epoxies are available in colors, but clear epoxy applied outdoors tends to yellow over time. High water resistance can trap water vapor in the concrete.
Usage Tips
Questions often come up as to which sealer to use for particular applications. Here are some helpful tips:
- If you want to protect decorative concrete work, look to a film-based sealer.
- Always check product compatibility for the type of surface you want to seal: a floor overlay, stained concrete, polished and dyed floor, etc. Using an inappropriate sealer can result in bleeding, blistering or bubbling.
- If you are most concerned about protecting an interior concrete floor from stains or scuffmarks, choose a sealer, such as polyurethane or epoxy, that creates a high-build protective film. These are especially good for high-traffic public locations, and they require less maintenance than acrylic sealers, which need periodic applications of wax or polish.
- If you are concerned about inhaling volatile organic compounds in a poorly ventilated area, gravitate towards water-based sealers instead of solvent-based ones. In addition, be aware that solvent-based concrete sealers are flammable and may have noxious fumes.
- Choose the sheen you want for the sealed floor. Those seeking a polished stone look should select a high- or medium-gloss sheen. Acrylic sealers give the widest ranges of sheens. If you don’t want a shiny surface, pick a sealer with a low-gloss or matte finish.
- The life expectancy of a sealer depends on its type, its maintenance and the amount of exposure it receives. Urethanes and epoxies can last for years and then might need to be reapplied. Other types will require more maintenance and quicker renewal.
Even the best concrete sealers aren’t very expensive, so use the best sealer your budget allows in order to maximize the benefit.