Concrete Efflorescence Solutions by SUNDEK

Learn how to address efflorescence on your concrete surface.

Posted on February 12, 2025 in Blog

Efflorescence on an interior concrete floor.

What is efflorescence?

Efflorescence, sometimes called Unreacted Calcium Carbonate, is a crystalline salt deposit that forms on the surface of concrete, brick, and stone. It creates a discoloration on concrete that looks like a white powder on the surface. Unfortunately, efflorescence can make a perfectly installed concrete job look terrible.

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What causes efflorescence?

Efflorescence occurs when moisture that contains salts passes through the masonry and evaporates, leaving salts behind. Most often, the moisture comes from underneath or behind the masonry, leaving the chalky residue.

Can efflorescence be prevented?

While contractors can’t completely prevent efflorescence, they can take steps to minimize the potential for it to arise:

Use low-alkali cement and aggregates
Use a well-designed mix that has a low water-to-cement ratio to reduce the concrete’s porosity
Add joints appropriately so that the amount of cracking is reduced, which will reduce the possibility of moisture getting trapped in the surface
Install 15mil vapor barrier beneath the slab with seams sealed
Use proper curing techniques to prevent too much moisture evaporating from the surface too quickly
Apply high-quality sealers to prevent water seeping into the surface

Even though these steps can minimize efflorescence, unfortunately it can sometimes still occur due to environmental factors.

How to address efflorescence when it occurs

Unfortunately, “there isn’t a simple solution to make it disappear or a magic wand to make efflorescence go away,” says Kevin Toczek, SUNDEK’s director of training and technical support.

However, Toczek offers techniques for minimizing efflorescence and reducing its impact on the appearance of a concrete surface.

Epoxy coatings

The right type of epoxy coatings can stop or reduce moisture drive from within the concrete. (Moisture drive is the process by which water vapor moves through concrete.)

Lithium densifiers

Using this surface strengthener can react with the salts, causing them to gel with the concrete, preventing more efflorescence from occurring.

Sealers

By sealing the surface with a high-quality penetrating sealer, you can slow the movement of salts. Using a penetrating sealer is key, as you don’t want to form a film on top that would trap the efflorescence.

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Tips on Color

If you want to color your surface to minimize the appearance of efflorescence, using lighter colors is key. Salts are less noticeable on lighter colored floors. Avoid darker colors which will draw attention to the efflorescence.

Cleaning Efflorescence

The method you use to clean a concrete surface that’s been affected by efflorescence depends on the location of your floor.

Interior floors: Clean with a microfiber mop with a diluted solution of water and vinegar. Clean floors weekly.
Exterior floors: Clean with a vinegar solution or light acid. Clean surfaces regularly.