What are the white stains on concrete blocks?

Author: Prof. Walter Huel Jr.  |  Last update: Monday, January 1, 2024

Efflorescence is a crystalline deposit of salts that can form when water is present in or on brick, concrete, stone, stucco or other building surfaces. It has a white or greyish tint and consists of salt deposits that remain on the surface after water evaporates.

Is efflorescence on concrete a problem?

Efflorescence alone does not pose a major problem, but it can be an indication of moisture intrusion, which may compromise the structural material. Building materials, such as concrete, wood, brick and stone, are porous materials. Porous materials can absorb or wick water by a process called capillary action.

What is the white stuff on my cement blocks?

This white substance is called Efflorescence. It generally shows up on surfaces like concrete, retaining walls, stone and even stucco. Efflorescence is a crystalline or powdery deposit of salts. It occurs when water leaves behind salt deposits on the masonry surface.

How do you remove efflorescence from concrete blocks?

Once the water source is eliminated, most efflorescence (also called Calcium Carbonate or limestone) can be removed with abrasive techniques. Dry brushing, light water blasting or light sandblasting followed by flushing with clean water. In large areas, rotary scrubbers with scrubbing pads may also be used.

Is efflorescence a serious problem?

It is common for people to confuse mold with efflorescence. Efflorescence itself isn't dangerous or harmful. It can lead to potential moisture problems that can cause structural damage to building materials.

How Do You Remove White Marks From Brick? | How Do I Get Rid Of Efflorescence?

Does efflorescence mean mold?

A few major differences between efflorescence and mold growth: Mold grows, efflorescence doesn't. Mold can grow on just about any surface, whereas efflorescence doesn't spread. Mold is a fungus, whereas efflorescence is moisture that evaporates into salt deposits.

Should I remove concrete efflorescence?

Ultimately, efflorescence itself isn't dangerous. However, it can lead to potential moisture problems that can cause structural damage to building materials. That means if you find efflorescence in the basement or on concrete and other structures, it's important to take action.

Will efflorescence eventually stop?

Efflorescence on pavers will eventually stop on its own after the salts in the pavers have dissipated. On the other hand, recurring efflorescence may indicate an ongoing problem of water intrusion that needs to be addressed before it causes permanent damage to the structure.

How do I permanently get rid of efflorescence?

As stated previously, most efflorescing salts are water soluble and many will disappear with normal weathering unless there is some external source of salts. In general, most efflorescence can be removed by dry-brushing followed by flushing with clean water.

Will efflorescence keep coming back?

Unless something else is done, the efflorescence will be back soon. In order to prevent it, you'll need to: Eliminate soluble salts for your concrete or masonry, and/or. Prevent water from transporting soluble mineral salts to the surface.

Does vinegar remove efflorescence?

The acidity in the vinegar helps remove the efflorescence and calcium deposits by breaking down mineral crystals. After cleaning the surface, let dry for 48-72 hours (moisture content below 25%).

How can you tell the difference between white mold and efflorescence?

The easiest way to determine if it's efflorescence is to spray water on the substance. If it's mold (or a spider web), it won't change much. If it's efflorescence, it will dissolve.

Will a dehumidifier help with efflorescence?

The truth is that a dehumidifier does nothing to counter or reverse the effects of efflorescence on your crawl space walls.

How long does efflorescence last?

This form of efflorescence generally lasts around two to three years and fades naturally as the salt supply decreases. 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.

When should I be concerned about efflorescence?

Efflorescence, in and of itself, does not necessarily pose a threat to you or your home's foundation; however, when accompanied by other signs and symptoms it should be seriously evaluated. Other signs and symptoms to look out for: Mold and mildew in your crawlspace. A musty/damp scent.

What is the white powder on my concrete block wall?

Efflorescence is actually a harmless crystallized mineral salt that has formed on your basement walls over time. It will generally look like a white, powdery substance. It's also commonly found on floors. In cases where moisture bubbles up from your basement floor, it may even resemble a white "foam" on your floors.

What is the main cause of efflorescence?

Efflorescence occurs when water soluble salts travel to the concrete surface. The mineral salts might be a result of the cement hydration reaction or can come from many other sources like sulphate rich sand. Porous concretes, masonry and mortars will be more susceptible to the migration of salts to the surface.

Will dish soap remove efflorescence?

To start the maintenance process, you can 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.

Does efflorescence affect strength of concrete?

Efflorescence is not a structural problem for the concrete, it does not affect strength or durability. But it is unsightly, and lowers the perceived value of the concrete. Efflorescence is usually composed of salts that are deposited on a concrete surface.

Does CLR remove efflorescence?

A: Yes. We recommend using a 50/50 solution (equal parts of CLR Calcium, Lime and Rust Remover and warm water.) Apply solution to the affected stained areas of the windows using a damp cloth or sponge.

Can you pressure wash off efflorescence?

Pressure washing can work to remove white efflorescence once the surface has thoroughly dried. The surface must be thoroughly rinsed to ensure that no residue remains. We also use a safe detergent to ensure a thorough clean.

What is the best efflorescence remover for concrete?

RadonSeal Efflorescence Cleaner can be safely used on poured concrete, concrete blocks, bricks, stucco, pavers, and artificial stones. The cleaner chemically breaks down and removes efflorescence, lime deposits, metal salt stains, and rust deposits.

Is efflorescence in basement a problem?

In terms of causing damage to your health, efflorescence is not dangerous. However, it is important to recognize that the appearance of efflorescence indicates that you might have a moisture problem in your basement. Left untreated, this moisture can cause structural damage and major headaches in the future.

What is the best concrete sealer to prevent efflorescence?

To do this, it is recommended that you treat your concrete walls with a breathable, penetrating concrete sealer like the Siloxa-Tek 8500. The Siloxa-Tek 8500 is able to prevent efflorescence from coming to the surface by reducing moisture intrusion and water infiltration.

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