Efflorescence 101: What is it? How do you remove it?

When a paver or wall project is installed, a powdery white deposit may sometimes appear on the surface. It can be alarming to see on your newly installed patio and may leave you asking, “What is this?” Your contractor or landscape supply store will tell you that it’s something called “efflorescence.” But what is this exactly? Is it something to worry about?

We’re here to tell you:

• it’s natural… (not a manufacturing ‘flaw’)
• it’s temporary

and, most importantly,

• it can be removed

What is it?

Efflorescence is a powdery, white mineral deposit that sometimes appears on the surface of concrete-based building materials and clay products. More technically: it is a naturally occurring calcium salt.

How does it appear?

When cement and water are mixed and chemically react, calcium hydroxide is produced. As the concrete dries, the calcium hydroxide reacts with the carbon dioxide in the atmosphere to produce calcium carbonate, which manifests on the surface as a white solid. Repeated exposure to wetting and drying accelerates the “wicking” of this calcium to the surface.

The occurrence of efflorescence in the pores of the concrete can lead to the appearance of white patches on the surface or an overall lightening of the paver, which is often mistaken for the product having stains or marks on it. Although the appearance of efflorescence can be worrying, rest assured the effects of efflorescence are aesthetic do not alter the strength or durability of the concrete pavers. Most importantly, they’re temporary!

When does it happen? And how do you get rid of it?

If efflorescence is going to appear, it generally happens within a couple of months after installation, and fades naturally with time, and after a season of rainfall.

It is possible to accelerate the removal of efflorescence by washing with a specialized efflorescence remover, a product that is specially formulated to dissolve efflorescence and remove ground-in dirt on paving stones and concrete, without discoloring or damaging surfaces.

• Start with Soap & Water. Depending on the amount of efflorescence, many homeowners simply use regular dish soap and water with a stiff plastic scrub brush. DO NOT use a wire brush, as pieces of wire can become dislodged and create rust marks on the surface of the product.
• Consider speciality cleaners. If soap and a stiff brush doesn’t remove all of the efflorescence, you can purchase an efflorescence remover, which is specially formulated to dissolve efflorescence and remove ground-in dirt on paving stones and concrete, without discoloring or damaging surfaces. These cleaners are available from most landscape supply dealers.

Efflorescence cleaners are typically acid-based, so proper mixing and application must be followed. Acid cleaners dissolve a thin layer of cement on the surface of the pavers, so the color of the pavement may change slightly, especially with thrumix pavers. Unilock EnduraColor facemix pavers can better withstand acidic cleaners. Always follow label directions for use.

As always, when using any cleaning solution, a small, inconspicuous area should be cleaned to test for surface and color reaction.

Should you have additional questions, we encourage you to reach out to your local Unilock Outdoor Idea Center, your contractor or landscape dealer.