Efflorescence 101: What is it?

After you install a paver or wall project, you may notice a powdery white deposit appearing on the surface. It can be quite alarming to see on your newly finished outdoor patio, and you may find yourself asking, “What is this?”

Rest assured, it’s a natural phenomenon known as “efflorescence,” and it’s nothing to be concerned about. Before you close the book on your next outdoor project, here are a few things to know about efflorescence and the best ways to clean your pavers.

What is efflorescence?

A powdery, white mineral deposit that sometimes forms on the surface of concrete, brick, stone or other porous surfaces. In technical terms, it consists of naturally occurring calcium salts.

Main causes

When cement and water mix and undergo a chemical reaction, calcium hydroxide is produced. As the concrete dries, this calcium hydroxide reacts with carbon dioxide in the air, resulting in the formation of calcium carbonate. This calcium carbonate manifests as a white solid on the surface. The repeated cycles of wetting and drying contribute to the migration of calcium to the surface, leading to the appearance of efflorescence.

Is efflorescence a serious problem?

Despite the appearance of stains or marks on the surface, it’s important to note that efflorescence will not compromise the strength or durability of your concrete pavers. Its impact is solely aesthetic and temporary in nature.

How do I permanently get rid of it?

If you wish to remove efflorescence, you can consider using a specialized efflorescence remover. These products are specifically formulated to dissolve efflorescence and remove dirt from paving stones and concrete surfaces without causing discoloration or damage.

To start the maintenance process, use a solution of regular dish soap and water along with a stiff plastic scrub brush. Avoid using a wire brush, as it can dislodge wires and create rust marks on the surface. If efflorescence persists, you can explore the option of using an efflorescence remover, which is available at most landscape supply dealers. Just make sure to follow the instructions carefully, as these cleaners are typically acid-based and may cause slight color changes on the surface. Be sure to test a small, inconspicuous area first to check for any adverse reactions.

Does efflorescence come back?

Efflorescence has the potential to resurface if the underlying conditions that initially triggered it persist, namely water infiltration. Inadequate patio drainage can lead to the continual seepage of water into the concrete, leading to the transportation of salts to the surface. As a result, the potential for efflorescence to resurface increases. It is crucial to remain vigilant for common indications of ongoing water infiltration, including the presence leaky pipes, compromised waterproofing, elevated groundwater levels, or inadequate drainage.

Will rain wash away efflorescence?

It’s worth noting that rain alone will not completely eliminate the problem, especially if efflorescence is deeply embedded, or if the surface is not exposed to consistent rainfall. In such cases, additional cleaning methods or treatments will be necessary to address the issue.

Do I need to remove efflorescence before applying a sealer?

Yes. Pavers must be clear of efflorescence before applying a sealant. If you choose to wait for efflorescence to fade away with time, it’s best to wait 2-3 months (or even up to one year) before sealing to ensure the efflorescence is completely gone.

If you have any further questions, we visiting a local Unilock Outdoor Idea Center near you, or speak to a Unilock Authorized Contractor for expert guidance and assistance.