Efflorescence in concrete - What can you do about it!

Dec 23, 2020

The crystals growing on the concrete surface can easily resemble small white blossoms. © MC-Bauchemie 2025

Predicting and avoiding efflorescence on concrete surfaces is no easy task. This MC-Pedia article lists and explains what to consider and how to reduce the risk of efflorescence.

These are our tips for reduction of efflorescence so you and your customers can enjoy the best possible looking concrete surfaces.

Use a cement with reduced alkali content!

On top of being able to create efflorescence forming salts themselves, alkalis behave as a sort of accelerating catalyst in the efflorescence process. The lower the alkali content, the lower the risk of efflorescence.

Wash freshly hardened concrete with clean water!

This washes off alkali from the surface layers. You can also use a brush if you want to keep the concrete dry.

Lighten up the concrete color!

Because efflorescence is much more visible on dark surfaces, using lighter colored concrete can help making it less obvious. While cements also have lower alkali content.

Use hydrophobic waterproofing admixtures!

Water-repelling admixtures significantly reduce or even completely prevent the migration of liquid water through concrete’s capillary system. Less liquid water means less efflorescence. No liquid water means no efflorescence.

>> Click here for MC waterproofing admixtures for normal concrete

>> Click here for MC waterproofing admixtures for semi-dry concrete

Use surface impregnations and coatings!

Both film-forming and non-film-forming surface protection can be used to further boost the surface impenetrability. They can be very effective, but require additional application steps and can alter the surface aesthetics.

>> Click here for MC surface impregnations

Use water absorbers!

Water absorbers are mostly utilized as rheology modifiers, but since they are effectively immobilizing water from participating in the efflorescence-forming processes and reactions, they can have a positive effect on the risk of efflorescence.

Don’t sleep on proper curing!

A good curing in the first hours and days of concrete hardening is critical when it comes to efflorescence. Preventing premature evaporation of water guarantees that it will have enough time to react with cement to create a dense matrix instead of generating additional capillary porosity.

>> Click here for the MC curing agents

Conclusion

In summary, the easiest and most reliable method for efflorescence prevention is a combination of low alkali cement, low water content, right plasticizing or compaction aid admixture, decent waterproofing admixture and good curing.