Solving Concrete Efflorescence

Solving Common Problems with Concrete: Efflorescence

Concrete is widely touted as a superb material for outdoor and decorative surfaces due to its strength, durability, and minimal maintenance.  However, there are some unique issues that may arise with concrete as it ages or settles. Most people know that concrete may crack or discolor over time, but a less well known issue is efflorescence, a white powder that can rise to the surface of concrete. This is a common issue that occurs with both plain and decorative concrete. Read below for more information on efflorescence, as well as how to prevent or remove it from your concrete surfaces.

What is efflorescence?

Efflorescence is made up of salt deposits that gather on the surface of concrete over time. Salt is commonly found in cement, as well as many of the aggregates used to mix concrete. Unless the concrete has been completely sealed on all sides, which is generally impossible when lying concrete on the ground, water will seep through the concrete material.

As water moves through the concrete, it dissolves the salt and carries it to the surface. Once exposed to the elements, the water evaporates, leaving behind salty residue. This process can be more significant in moist conditions, such as humid regions, rainy climates, or automatically watered lawns. As this process continues, the buildup can become significant. Efflorescence is generally not noticeable on plain concrete surfaces. However, it can be quite visible on patterned or colored concrete surfaces and mar the design significantly.

How to remove efflorescence

Most of the time, efflorescence is a light powder that washes off in rain or can be removed with a hose or broom.  However, if it is not removed, it can eventually harden and become harder to clean.

Salt that has been dissolved and re-deposited multiple times can crystallize and harden on the surface of concrete. This can result in white patches or an overall whitening of the concrete area. Crystallized or dried-on efflorescence may be able to be removed with power washing or scrubbing with a brush and mild soap. For particularly difficult stains, you may need to use a specialized concrete cleaner that is recommended for efflorescence and other tough stains.

If no other solution works, you can use an acid solution. However, acid solutions should not be used unless absolutely necessary, as they can deteriorate the surface of the concrete, as well as any patterns or designs. Also, it must be neutralized after use, and then it is recommended that you reseal the concrete surface. If you do use an acid solution, follow all instructions carefully and wear protective gear.

How to prevent efflorescence

Proper installation and maintenance of concrete can help to prevent efflorescence from occurring or returning. Effective drainage solutions are extremely important in order to keep moisture away from the concrete. This can include drainage underneath the concrete or away from the area. Ensure that no drainage from other sources, such as downspouts, empty onto the concrete surface.

Most concrete sealers are very effective against efflorescence. They prevent moisture from entering the concrete surface, though moisture may still come from underneath. This can cause efflorescence to build up underneath the sealant, which is incredibly difficult to remove. If efflorescence is likely to be a problem, a penetrating sealer is the best choice. This not only provides a barrier to moisture at the surface, but also flows through the concrete, eliminating pathways through which moisture can travel.

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