Efflorescence on concrete

Efflorescence is usually found on ordinary masonry, but can also occur on concrete components. Although both are efflorescence, they do not have much in common at first. Below we go to the efflorescence on concrete.

Efflorescence on plaster or masonry

Efflorescence on a traditional masonry is usually nothing unusual. Especially in cellars of old buildings, these are very often seen. These are salts that are partly in the masonry, but also rise with the moisture from the soil. When transported to the surface of the masonry, the salts begin to crystallize. The danger is that these salts may, among other things, destroy the cement.

Efflorescence on concrete has another cause

This type of efflorescence is often equated with the white discolorations on concrete surfaces. However, these are not salts. Rather, these efflorescences in concrete have to do with the natural building materials of concrete and their composition. Concrete consists of the following substances:

  • cement
  • water
  • Aggregate (formerly surcharge)
  • possibly concrete additives
  • possibly concrete admixtures

The limestone contained in the cement is responsible

In particular, the composition of the cement is now important. This consists among other things of fired Portland clinker, clay and limestone. Anyone who ever wanted to produce watertight concrete knows how complex it is. Even if concrete is only very weakly absorbing water, the composite construction material has pores. The water can then penetrate through the pores (which is why concrete is not frost-proof, by the way).

As a natural product, the lime content in the cement may vary

Whether it comes to efflorescence on the concrete, depends essentially on the cement used. The limestone content is crucial here. Most of the limestone is bound. However, if the amounts of limestone fluctuate, an unbound surplus may also be present. This limestone can then trigger the penetrating water in the concrete. This solution now diffuses slowly to the surface. The water evaporates leaving the white limescale behind.

What to do against the efflorescence of the concrete?

Bound lime can not dissolve the water. Therefore, in principle, only the excess lime is removed. This in turn means that the concrete efflorescence can only be observed in young concrete components. As a rule, these are not older than 5 years and must also come into regular contact with water. It can be concluded that the lime efflorescence on the concrete are completely harmless.

The efflorescence of the concrete will be self-evident over time

If it comes to efflorescence, then mostly to concrete parts that are exposed according to the weather, for example, concrete tread stones, paving stones or foundations. Most of these efflorescence can be observed over a maximum period of two to three years. By then, most of the excess limestone is completely released from the concrete.

Tips & Tricks

Even if the efflorescence on the concrete is not dangerous or harmful to the concrete, it is at least unpleasant and not nice to look at. If you do not do anything, sooner or later the limescale deposits will be swept away by the rain and melt water. You can also remove the deposits yourself. Brush the affected areas and rinse with clear water. If you want to stop the efflorescence, you can seal or impregnate the concrete.

Video Board: Efflorescence Tips and Tricks