Efflorescence in concrete - What can you do about it!

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.

Reduce the permeability of your concrete!

• Plasticizers and superplasticizers have a dual effect. They allow a reduction of total mixing water while still improving compaction. This can lead to significantly less porous and therefore more waterproof concrete.
• Pozzolans such as fly ash, microsilica, metakaolin, or GGBS lead to precipitation of pore-filling secondary C-H-S gels. As a bonus, this reaction also consumes Ca²⁺ ions, preventing them from becoming the source of efflorescence.
• Crystalline waterproofing admixtures and additives consume the Ca²⁺ ions that would otherwise be converted into efflorescence to seal pores via crystallization.
• Curing in a CO₂ rich atmosphere seals the concrete surface via (controlled) accelerated carbonation. This method is, however, rather complicated and expensive.

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