Efflorescence … What’s this white stuff on my paving?

Efflorescence is a white residue that looks like a white powder on top of the pavers or a white scum type smear in the paving brick.

Efflorescence is seemingly prevalent with all types of paving and while its presence on a recently laid patio or driveway can disappoint the homeowner, they sometimes feel that the usual disclaimer from the manufacturers \”efflorescence is a naturally occurring phenomenon… … blah, blah, blah … can accept no responsibility … blah, blah, blah … will disappear in time\” is less than reassuring and to some, it reads like a cop out, an excuse, a way of washing their hands of what is, after all, a visually distressing and disappointing problem.

To be fair to manufacturers, they are stuck between a lump of concrete and a hard place. Try as they might, there\’s very little they can do to control the appearance of efflorescence, and what few technical fixes are available do tend to be employed by many of the better manufacturers. It\’s in their own interest to attempt to minimise the incidence of efflorescence, but even if they used every trick known, if they use efflorescence-reducing additives in the freshly mixed concrete, if they introduce steam to the curing chamber, or whatever other strategy is employed, there is no way they can guarantee that efflorescence will not be a problem with their products, because efflorescence is a naturally occurring problem and the chemistry involved is complex, involving a number of factors over which neither the manufacturer, the contractor, nor the homeowner has any control.

So: what can be done to reduce the visual impact of efflorescence, or to speed its departure? There\’s a wealth of anecdotal advice out there, much of which is dubious, while some is downright dangerous, but there are some tried and tested \’tips of the trade\’ that are worth trying, even if they don\’t completely resolve the problem.

What is efflorescence

In simple terms, Calcium Carbonate is a by-product resulting from an interaction between the cement used to manufacture the paving and the natural environment, which includes the ground, the weather, and the atmosphere. The result is a deposit or \’salt\’ that appears on the surface of the paving. There\’s no single, definitive appearance – it is sometimes powdery, sometimes scummy: sometimes it\’s hazy and indistinct; sometimes it\’s sharp, crisp and obvious. Sometimes it covers large expanses or paving, sometimes it affects individual units, and sometimes it affects just half or two-thirds of a paving unit. It seems to affect dark hued pavings more than those of lighter tones, but the truth is that it\’s just more noticeable against a darker background.

How long will it last

This is the tricky question. No-one can say how long any incidence of efflorescence will last. It might be a few weeks; it might be a couple or three months; it could be a year or two. There are so many factors affecting its generation and appearance, and its disappearance that an educated guess is the best we can manage. We know that certain conditions have an effect: damp, shady sites can be more adversely affected than open, sunny sites, and, for some reason, the phenomenon always seems worst when the daffodils are out, which must be linked to climatic and ground conditions in some way, but no-one is really sure how.

How to clean it

There\’s no documented way to remove efflorescence, but the following may help speed up the process of this natural occurrence disappearing. No doubt that some of the proprietary products do remove the visible salts from the surface of the paving, but it is a temporary fix – the problem is very, very likely to return.

For cement pavers and or pavers with coloured oxides: A non-chemical strategy involves regular brushing and rinsing with clean water. This helps remove both soluble and insoluble products of efflorescence and may actually accelerate the eventual permanent disappearance of the deposits. There have been suggestions that a few drops of wash-up liquid added to each bucket of water can also help

Clay pavers: Again, the deposits can be washed off with a stiff brush and clean water or left for nature to sort out. On flexible pavements, heavy deposits can be dispersed with the aid of a dilute acid wash. Unlike concrete products, the colour of clay pavers is natural, permanent and unaffected by low-strength acid washes, but care is still needed, and any acid-based treatments are best used as a last resort and as infrequently as possible. Most manufacturers of clay pavers do not recommend the use of acid-based cleaners, and it\’s worth following this sound advice.

Links to further sites that can be viewed:

http://www.dehoopsteenwerwe.co.za/information02.html