Can You Seal Old Concrete?

Concrete is an ideal material for many building projects because of its natural durability. As it ages, though, the concrete can get marks and stains that are hard to remove. A coat of protective seal can protect it from stains that come from mildew, environmental stressors, oil, salt, and other corrosive substances.

The concrete doesn’t even have to be new for the sealer to work! Older materials can be sealed for the first time or resealed if a protective layer has been applied in the past. Here’s how you can seal concrete for the first time or renew the coat for the best protection.


Removing Old Sealer

sealing old concrete - fiorinoIf the concrete has been previously sealed and this layer is worn out and damaged, you have to remove the old protection before adding a new layer. If it has a coat already, remove the older sealer with acid etching or grinding. While acid etching is easier, you should only use it with proper care. You spray a diluted muriatic acid on the concrete, then neutralize it before washing it down. The combination of acid and pressure should take the older coat off quite easily. Make sure to let the slab dry completely before applying the new sealer.

You may be able to reseal without removing the previous sealer. For instance, you can apply a solvent-based acrylic sealer on top of a layer of solvent-based acrylic sealer. This is only safe if you know what sealer is already on your concrete; if the home is new to you, it’s usually best to strip the concrete.


Cleaning And Repairing The Concrete

concrete sealing - fiorinoOnce you have removed the old sealer or have confirmed it’s in good enough condition to work with an additional layer, the next step is to clean the surface. You should scrub off all mildew, rust, grease, and other unwanted materials before sealing the concrete because you don’t want these substances sealed in. Acid etching or grinding the concrete should give the concrete a suitable surface profile for epoxy floor coating.

When the concrete is clean, patch up any cracks with a suitable repair product. If the concrete has severe pitting or spalling, consider using a concrete overlay to resurface the existing concrete before adding the sealer. The overlay is a thin layer of concrete mixed and applied on top of an existing slab.


Resealing Old Concrete

concrete wall - fiorinoWhen you have repaired and prepped the concrete, you can add the sealer. When choosing a sealer, determine the type of protection you need. For example, if you are resealing a driveway that gets a lot of damage from road salt, use a salt repellent sealer; if you are looking to seal the interior walls or floor of your basement, use a waterproofing concrete sealer.

Once you have selected the sealer, be sure to follow the instructions. Generally, you should apply the product in thin coats, letting each one dry before applying another. It’s easy enough for homeowners to do themselves, and the result will protect your concrete for years to come!

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