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What is Concrete Sealer?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

Concrete sealer is a compound used to protect concrete from the elements. Concrete is a porous material, and without sealing, it will freely breathe. It will also absorb water, which can lead to a variety of structural and aesthetic problems. Many home supply stores carry sealers for people working on concrete projects at home, and it is also possible to purchase them through contracting suppliers and specialty companies. Concrete should not be left unsealed, except in certain circumstances.

There are two ways in which a concrete sealer can work. Film forming sealers work by creating a barrier in the form of a layer of waterproofing on top of the concrete. As long as the sealer is in good shape, the concrete underneath will stay dry. It is also possible to buy penetrating sealers that soak into the material to waterproof it. Some sealers also include a stain that is used to color the concrete, while others are clear.

A man smoothing out a concrete floor.
A man smoothing out a concrete floor.

The primary difference between these types of sealer has to do with the look of the finish. If a glossy or wet-looking finish is desired, film formers should be used. Matte finishes can be accomplished with penetrating sealers. In both cases, the compound may need to be periodically stripped and reapplied to keep the concrete in good condition. Some signs that it needs to be resealed include staining, scuffing, and increased moisture in the concrete.

Concrete sealer can reduce the risk of cracks.
Concrete sealer can reduce the risk of cracks.

Using a concrete sealer prevents water from penetrating the material, reducing the risk of cracks and other types of water damage. Stains are also greatly reduced, which helps to keep floors and other concrete installations looking cleaner. Preventing staining and moisture can discourage the growth of moss, mold, and plants that might use the concrete as a substrate. Sealed concrete also resists chemicals and corrosion, making it useful for kitchens and scientific laboratories.

Scientific laboratories may benefit from having sealed concrete floors.
Scientific laboratories may benefit from having sealed concrete floors.

In outdoor installations like driveways and paths, some people prefer not to use concrete sealer. The breathing properties of unsealed concrete allow water to percolate through, rather than running off, which preserves rainfall, snow melt, and other sources of water. Permeable walkways, driveways, patios, and other outdoor installations help to keep water around the home and garden, which can be useful in regions that are prone to droughts. The unsealed concrete, however, will tend to break down more quickly, so it may need to be replaced more often.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AboutMechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AboutMechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...

Discussion Comments

anon132083

One point I think you might have missed:

Concrete sealers will also protect concrete from deicer materials, which can increase the freeze-thaw cycle of water inside of concrete. As that water expands and contracts, it will break the concrete surface down. Additionally, the deicers will remain in the concrete as the water evaporates, crystallizing underneath the surface and creating pressure that will make the surface chip and split.

Sealing these concrete surfaces will protect them from that kind of damage, leading to longer-lasting, more attractive concrete. I recommend Concrete Treat for these kinds of applications. You can order it online.

anon81299

we have an area around our house and patio that has been concreted, but has very loose dust surface, and when you walk from outside to inside you leave white footprints on the tiled areas. is this a health issue?

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    • A man smoothing out a concrete floor.
      By: Lilyana Vynogradova
      A man smoothing out a concrete floor.
    • Concrete sealer can reduce the risk of cracks.
      By: Taweesak Ngamamornpi
      Concrete sealer can reduce the risk of cracks.
    • Scientific laboratories may benefit from having sealed concrete floors.
      By: .shock
      Scientific laboratories may benefit from having sealed concrete floors.
    • Sealed concrete resists corrosion and chemicals, which makes it ideal for kitchens.
      By: Elenathewise
      Sealed concrete resists corrosion and chemicals, which makes it ideal for kitchens.
    • Wet concrete being poured.
      By: uwimages
      Wet concrete being poured.