How to Minimize and Remove Concrete Efflorescence

Dark gray, rectangular concrete pavers with lighter areas of efflorescence.

Wausau Tile - Efflorescence In Concrete Pavers PDF

Efflorescence can be a very difficult problem for any concrete contractor or homeowner to deal with, and it can become quite tough to remove. When salts and other materials come off the concrete surface, they may leave stains.

These types of stains are generally white and stand out against darker backgrounds than light or pale hues due to the contrast of the chemical reaction. This article will look at the causes of efflorescence and what you can do to prevent and remove it.

What is Concrete Efflorescence and What Causes it?

Dark gray, rectangular concrete pavers with lighter areas of efflorescence and white specks.

Wausau Tile - Efflorescence In Concrete Pavers PDF

Efflorescence is a white deposit on concrete due to moisture loss. It's an issue that affects new concrete, in which sodium and sulfate chemicals from several hydroxides, minerals, chlorides and nitrates accumulate on the surface and pores of the material.

It's caused by water evaporation and is most common on darker-colored concrete and manufactured surfaces. Low temperatures, humidity, condensation and rain are all causes of efflorescence.

Two Main Types That Affect Concrete

Primary Efflorescence

When salt is added to concrete or clay products, it dissolves or is carried by capillary action to the surface. It becomes noticeable when the water evaporates. This form of efflorescence generally lasts around two to three years and fades naturally as the salt supply decreases.

Secondary Efflorescence

Salts are carried to the surface of concrete or brickwork by hydrostatic pressure or osmosis/evaporation, and deposited when the water evaporates, resulting in this type of efflorescence. This form of efflorescence continues as long as the supply of salty water remains constant.

Where Does it Come From?

Gray square concrete pavers with lighter discolored areas of efflorescence.

Wausau Tile - Efflorescence In Concrete Pavers PDF

Water — rain, humidity or groundwater — that penetrates the concrete dissolves latent salt and causes efflorescence. The sun draws the salt in solutions to the surface, and as moisture evaporates, it is deposited on the surface.

There's no need to be alarmed that your concrete products are damaged or faulty — they're going through a natural process that happens in all cement-based goods. With time and exposure to weather conditions, the situation will usually improve on its own.

How Does it Happen?

Concrete products, like masonry or tile, for example, contain cement, which generates lime or water-soluble calcium oxide. Lime can also be found in sand bedding and aggregate base materials, as well as soil. Although concrete products are robust, strong and extremely dense, they include millions of tiny capillaries that run from the interior to the outside.

These tiny capillaries are permeable to moisture from rain, sprinkler systems, subterranean sources, poor site drainage or fog. Calcium oxide reacts with the water in the capillaries to form calcium hydroxide. This rises to the top and combines with ambient carbon dioxide to produce a white cloud of calcium carbonate. When moisture on the surface evaporates, white efflorescence appears as a hazy film.

Minimizing Concrete Efflorescence

There are various methods for minimizing concrete efflorescence. One is to apply a sealer to the concrete. This will help keep the water from seeping through and will also help prevent salt crystals from forming.

A before image of gray concrete pavers with a tile lighter than the rest due to effloresence.

Wausau Tile - Efflorescence In Concrete Pavers PDF

Efflorescence Can Also Affect Concrete Pavers

Any formulation of concrete can develop efflorescence, including pavers. At Wausau Tile, we craft premier architectural products that utilize concrete. Both our precast concrete and concrete pavers can undergo efflorescence as this is a natural event occurring with concrete, but in no way does this compromise structural integrity.

In fact, concrete efflorescence typically does not persist past 18 to 24 months after production, depending on the climate. However, if concrete efflorescence has already formed, follow these procedures to remove it.

How to Remove Concrete Efflorescence

Under normal conditions, efflorescence on concrete can usually be removed with commercially available cleaners designed for concrete, which should be done as soon as possible after efflorescence appears and by strictly following the label warnings and instructions. Most cleaners include acid and detergent, so pay attention to all label directions and environmental rules. Improper or careless cleaning of the surface of concrete can lead to permanent bodily harm, concrete damage or discoloration.

Always test a small, inconspicuous region before applying any cleaner to the entire area being worked on. The concrete should be completely dry and free of efflorescence after cleaning, before any sealers are applied.

An after photo of gray concrete pavers once effloresence has been removed.

Wausau Tile - Efflorescence In Concrete Pavers PDF

For more information, you can also read more about efflorescence and our concrete products at Wausau Tile here.

Wausau Tile Manufactures Premier Architectural Products

For more than 60 years, Wausau Tile has demonstrated its dedication to quality, value and American craftsmanship. Our architectural pavers, site furnishings and custom precast concrete and terrazzo are unrivaled.

We're more than a manufacturer of exceptional architectural goods — we're a creative, engaged manufacturing partner that helps you every step of the way. Contact us today for more information.