Efflorescence

It is normal for efflorescence to occur on concrete products. Efflorescence can appear on the surface of concrete tiles/pavers due to a reaction between the lime present in the concrete and water. This phenomenon is inherent to cement-bound materials. Influenced by climatic conditions and daily use, this white deposit will diminish over time and eventually disappear. This process can sometimes take up to six months, depending on the circumstances. This white deposit is caused by natural reactions and cannot be prevented.

What is the white deposit?

Concrete is made by mixing sand, gravel, cement, and water. It is therefore essentially a natural product. With natural processes, you cannot control all factors. Nature runs its course. In concrete, the cement component of the four basic components is the 'culprit'. This can form a chemical reaction with water, creating free lime, which deposits on the concrete surface. The lime deposit then reacts with carbon dioxide from the air, resulting in calcium carbonate. This is how the white stains appear on the paving.

When does it occur?

There are two situations in which white deposit can occur: during production, due to the mixing water (primary efflorescence), or later due to weather influences (secondary efflorescence). Primary efflorescence rarely, if ever, occurs. The excellent compaction of the mortar and the low water-cement ratio work very favourably in counteracting white deposit. Primary efflorescence during concrete production is therefore ruled out. If a product suffers from white deposit, it is because the chemical reaction between cement and water continues after production. During storage or after placement, the tiles can absorb an excess of water, especially during rain showers or prolonged droughts, which is then sealed off after the shower. The result: secondary efflorescence.

What can be done about it?

There is practically nothing you can do about white deposit. The resulting calcium carbonate is virtually impossible to remove from the concrete surface without damaging the paver itself. The only thing that helps is patience, because in most cases, the white deposit will eventually disappear by itself. Due to the carbon dioxide in the air, the calcium carbonate slowly changes into a substance that is soluble in water. The problem thus resolves itself. It has now been shown that acidic contaminants in the air, such as carbonic acid and sulphur dioxide, accelerate these processes. In other words: white deposit disappears faster in areas with a lot of industry than in areas with pure sea and mountain air.