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Efflorescence – What is it, Causes, Removing & Prevention

What is Efflorescence?

Efflorescence is a deposit of mineral salts on surfaces of concrete and masonry walls and/or floors.  It is whitish in appearance, and is sometimes referred to as “whiskers”.


Causes of Efflorescence

Efflorescence occurs when water soluble salts travel to the concrete surface.  The mineral salts might be a result of the cement hydration reaction or can come from many other sources like sulphate rich sand.  Porous concretes, masonry and mortars will be more susceptible to the migration of salts to the surface.  Also, if there is a high concentration of mineral salts in the concrete there will be a higher chance of efflorescence. When the salt rich water migrates to the surface the water evaporates leaving behind a salt deposit causing the white staining of the surface.


What can happen after Waterproofing is laid?

Once the waterproofing is installed rainwater cannot soak into the substrate any longer and is held above it.  This means that the water which passes through the porous grout (and possibly the unglazed tiles), saturates the screed and/or tile adhesive bed.  Once the rain stops, the moisture in the screed/adhesive/grout evaporates from the upper most surface (tile surface), until it reaches an equilibrium with the air.  When the water evaporates it leaves any salts that may have dissolved from the screed/adhesive/grout behind as efflorescence.


How to remove the Efflorescence

The easiest way to remove efflorescence is to wash the substrate and scrub the area to see if the stains disappear.  Only clear water should be used to avoid worsening the situation.  The sooner the attempt to remove the stains, the better, as time will be against you.

It is very important to use a wet vacuum or have air blowing from a fan on the area, to remove all standing water.  If you try the above and don’t get any result, then the next step is to use a non-metallic brush to dry brush the area.  Once the brushing is completed, remove the loose salt using a scraper.

A solution of vinegar, muriatic or citric acid can also be applied over the affected area to assist with removal.  Dilution of these acids before using them is a must and be sure to always wear the required personal protection equipment (PPE).  If this option is used to remove the efflorescence, baking soda or any other similar alkaline product needs to be applied to the area, to neutralise the acidity on the concrete surface.

There are other commercial products available that can be used to remove the efflorescence in concrete, but ensure all cracks and joints are properly sealed.  When using these products, always try the product on a small area first, to verify that it will work and will not deteriorate the concrete.


How to avoid Efflorescence

The best way to avoid dealing with efflorescence is to prevent it from happening.  In order to minimize these issues, be sure to reduce alkali sulphate content of concretes or grouts, reduce lime content by using a class-F fly ash, keep a low water to cement ratio and ensure proper compaction to reduce voids and potential pathways for water migration.


For any other advice of a technical nature, Wet-seal’s highly experienced Technical expert – Robert Rath will be happy to take your call.  Rob can be contacted on 0413 008 303 or via email rrath@wet-seal.ws

Alternatively, please speak with your local Franchisee directly.  Details of your local Franchisee can be found at http://wet-seal.com.au/find-a-franchise/