A few months ago, you had your concrete floor sealed or polished. It looked fantastic until these white spots started to form. They kind of looked like watermarks. They were difficult to clean, maybe even impossible. You’re almost at your wit’s end trying to figure out how to deal with this: Efflorescence.

The white, circular discoloration is a clear example of efflorescence.


What’s happening is efflorescence, a mineral salt residue that’s the byproduct of moisture leaving the slab. This is a natural process that is perfectly normal. There are a few reasons why this could happen.

  1. There is no vapor barrier under the slab. It’s sitting directly on the ground. Older slabs often lack a vapor barrier, which allows for mineral salts in the soil to come through the concrete slab.
  2. The floor was fully polished or sealed too soon after the slab was poured. While concrete cures, it releases water and salts as it dries and hardens. If the concrete slab is still in this stage of curing when the polishing or sealing process takes place, efflorescence will occur.
  3. The polishing process took place before the building was conditioned. Concrete slabs cure evenly in a climate-controlled environment. When a worksite is still open when the polishing takes place, the variability in the weather and humidity will affect the slab. It can create conditions that will contribute to efflorescence.

Can it go away?

You can create conditions to remove the moisture from the slab if there is a vapor barrier in place. In a fully climate-controlled environment, the floor will continue to release moisture. This process can be sped up with the use of dehumidifiers.

It is also possible to clean the floor with products designed to remove mineral buildup. A professional janitor supply company will have a good idea on what is best for your needs. We use “Haze Away” from Janitor’s Supply Company, located here in Ft. Wayne, IN. An auto scrubber or swing machine will help rinse the mineral residue from the surface.

If the floor has been polished, the concrete may require the removal of the polishing guard product, to clean this residue and reapplied. If the floor has been sealed with a topical sealer (like acrylic or clear epoxy coating), then the sealer will need to be removed to clean the surface. The efflorescence is trapped between the concrete slab and the topical sealer.

Although unfortunate, effloresce is a natural process with many variables, and not a result of the polished concrete process.

The efflorescence removed with the right products and a mechanical clean.

Want help?

Our Project Leaders can help you navigate how to get your concrete floor looking its best. Our StrongTread ReFresh system is designed to make a well-loved polished floor look new. It includes a deep clean of the floor before bringing the floor back up to its original shine.