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What is Efflorescence

Efflorescence on pavingEfflorescence is the formation of salt deposits, usually white, on or near the surface of concrete and clay bricks, causing a change in its appearance. Apart from the discolouration efflorescence is harmless. This is best described as being ‘a temporary skin problem and not a deep-seated disease’.


In Gauteng, efflorescence is most obvious in the rainy summer months, but may be observed throughout the year, especially in irrigated areas and after a sudden drop or rise in temperature. It can occur from within the concrete or from the subgrade (soil below the pavers). With time, efflorescence becomes less extensive and in most instances it disappears completely. Light coloured pavers might show the deposit less than darker coloured pavers.


Efflorescence is a natural phenomenon that occurs through one or a combination of the following processes.

  • Chemical processes

Formation of efflorescence can be the result of a reaction of concrete constituents with carbon dioxide and/or sulphurous gases.

  • Physical processes

The formation of efflorescence could be caused by a number of physical processes involving both salt and water transfer in and out of the concrete product, the aggregates used in installation and the subgrade or earth beneath the pavers.


Efflorescence is very difficult but not impossible to remove.

Irrespective of the method used to clean efflorescence, it could re-appear (in some instances more severely than before).

In many instances rain will simply wash away white efflorescence.

Some recommend dry brushing and the avoidance of water to clean effloresced pavers.

Some recommend washing with clean water or a mild detergent.

A proven yet risky method of cleaning efflorescence involves the application of a mild acid solution to the pavers. (One part pool acid with 12 parts water.) Thorough pre-soaking and post washing with clean water is required when using this method. Pre-soaking reduces natural porous tendencies, limiting the depth of penetration of the cleaning solution. Post-washing is required to remove any residue of the acid.


Efflorescence is a natural phenomenon appearing randomly in most materials used for segmented paving. As mentioned earlier it could even be caused by the earth on which the paving is laid. Bosun Brick and other companies are actively working to find a remedy for efflorescence.

Many paving installations have never been affected by efflorescence. Some have had efflorescence for a few weeks while others have been affected for months. Sometimes efflorescence is recurring and sometimes it happens only once.

Bosun Brick cannot guarantee efflorescence-free products. (Prior to- or post-installation.)

Bosun Brick’s comprehensive Five Year Guarantee does therefore not cover efflorescence.

Remember, White Efflorescence is usually a temporary problem.

Contact Us

Head Office
Cnr Cresset and Musket Roads
Midrand Industrial Park
Phone: 011 310 1176
Email: info@bosun.co.za