What Causes Driveway Pavers to Go White?

Causes of Efflorescence

• Concrete is a material that absorbs groundwater and any mineral salts that may be present in the water. Mineral salts include chlorides, nitrates, chromium as well as other salts. The water moves the salts throughout the structure’s multiple channels. When the humidity is high outside, the salt is carried to the surface of your driveway pavers and is visible. Efflorescence is also known as “whisker growth” because the salt looks like gray hairs on your pavers’ surface. The salt buildup can also appear in columns on the pavers’ surface. If the humidity is low outside, salt deposits are left below the pavers’ surface and are not visible.

Concrete Mixing

• If a natural source of water, like from a stream, river or lake, was used when mixing the concrete to form your driveway pavers, effloresence could appear. The water may have been in contact with soil containing sodium and potassium salts. These salts are mixed into the concrete and will eventually rise to the surface and become visible due to water movement and humidity.

Efflorescence Cycle

• Efflorescence appears during seasons of high humidity and rains including after a rainy winter, spring or fall. You may not notice any salt buildup on your driveway pavers during the summer months. The efflorescence cycle may repeat itself for months or years and then disappear completely. Only in extreme cases will it reappear after being gone for years.

Removing Efflorescence Manually

• Cover any landscaping around the pavers to keep salt, dust and dirt off the surfaces. Brush off the white film with a stiff brush and then spray the pavers with water to remove the efflorescence. Wipe the pavers with an old towel or rag to remove any caked-on dust or dirt. Brush off and spray your driveway pavers regularly to keep the efflorescence from returning.

Using a Chemical Cleaner

• You can also use a commercial efflorescence cleaner on your pavers, available at hardware, home improvement, concrete and outdoor supply stores. Wear rubber gloves and a nose mask when handling and using the chemical. Wet the pavers with water first. Apply the cleaner to an old towel or rag and then wipe the pavers with the cleaner-soaked towel or rag. Spray the pavers thoroughly with water to restore the concrete’s shine.

Cautions and Sealing

• Do not use muriatic acid to remove the white film, dirt and dust. The acid is too powerful for the concrete and will damage the pavers. Do not use a commercial cleaner that doesn’t clearly state it will remove efflorescence and clean concrete surfaces. Purchase a commercial sealer designed for concrete, to reduce the amount of salt escaping your driverway pavers. Apply the sealer evenly with a paint brush or roller after removing the white film and any dirt from your driverway pavers. Follow any recommendations on the sealer’s container. Commercial sealers are also available at hardware and home improvement stores as well as concrete and garden supply stores.