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Dealing with Efflorescence?

Paving Slabs(400mm x 400mm x 50mm) in Kampala Uganda

Little background

Is there a white residue covering some of your pavers after months or weeks it was installed? Before you panic and think your pavers are ruined forever, we urge you to read this article to the end. This white cloud that you see is called Efflorescence and is not as worrying as it may first look. According to studies done in the USA about 5% of all concrete experiences Efflorescence in its lifetime.

What it is?

Efflorescence is a naturally occurring that sometimes appears on the surface of cement-based materials such as Paving, vibracrete walls, Slabs, and pretty much any other concrete product. As cement and weather chemically react together, calcium hydroxide is produced. In certain rare conditions as the concrete dries, the calcium hydroxide may react with the carbon dioxide in the atmosphere to produce calcium carbonate, which manifests as a white residue. Although the appearance can be worrying at first the effects of efflorescence are purely aesthetic and temporary. It does not alter the concrete’s strength or durability, and the pavers will return to their natural color over time.

Where does it usually occur?

Efflorescence is extremely difficult to predict and can occur in any condition on concrete products. That is why no manufacturers can guarantee that their goods will be Efflorescence-free for their lifetime. Based on chemistry this is purely impossible as any concrete product contains cement and lime which are all required for Efflorescence to occur. This phenomenon seems to occur mostly on Dark Pavers such as Charcoal in areas with a large amount of Lime or Salt present. It is also important to note that pavers should not be laid on soil instead of sand, this is due to the fact that soil has a lot of minerals in it which can badly affect Efflorescence.

What do we do as a manufacturer to limit the effect?

* reduce the amount of water used in the concrete mix, and so minimize the opportunity for Calcium Hydroxide to migrate during the initial curing process.

* employ additives that work within the fresh concrete to minimize the formation of the salts.

* slow down the curing process to encourage the formation of the insoluble Calcium Carbonate within the paving, and so create an internal barrier to the migration of dissolved salts.

* Keeping the pavers humid during the first couple of days of the curing process.

Although we do all that we can to avoid the natural occurrence of Efflorescence, about 5% of customers will experience Efflorescence in the lifespan of the paving.

How long will it last?

This has been a very difficult question for science to answer. It depends on many factors. Sometimes it can be a couple of weeks to months. It can even take a year for it to disappear naturally.

Should I be worried?

Not really, this phenomenon is site dependent and only occurs on about 5% of the sites. If you are part of that 5% minority, just remember that this effect occurred naturally and will disappear naturally. You just have to give it sometimes. Remember that your pavers are not defected forever and the color of the pavers will return to their normal state soon.

How to clean it?

There is no specific way that guarantees it will get rid of Efflorescence. One thing clear is that it will disappear over time. So, it is best to let natural wear take its course.

Last modified on 15/07/2023

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