Information: Efflorescence
White efflorescence Efflorescence 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”.
Efflorescence on Bosun Pavers 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 sub-grade (soil below the pavers). Over time, efflorescence becomes less extensive and in most instances, it disappears completely. Lightcoloured pavers might show the deposit less than darker-coloured ones.
How efflorescence occurs 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 sub-grade or earth beneath the pavers.
Removal of white efflorescence • • • • • •
Efflorescence is very difficult, but not impossible to remove. Irrespective of the method used to clean efflorescence, it could reappear (in some instances, more severely than before). In many instances, rain simply washes away white efflorescence. Others recommend dry brushing and the avoidance of water to clean effloresced pavers. Some recommend washing with clean water or a mild detergent. A proven, but risky method of cleaning efflorescence involves the application of a mild acid solution to the pavers (one part pool acid to 12 parts water). Thorough pre-soaking and post-washing with clean water are 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.
Bosun’s take on efflorescence • 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 in other cases, it happens only once. • Bosun Brick cannot guarantee efflorescence-free products (prior to- or post-installation). Bosun Brick’s comprehensive five-year guarantee therefore does not cover efflorescence. Remember, white efflorescence is usually a temporary problem.
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