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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 https://wet-seal.com.au/find-a-franchise/

Edition 2 – Other Causes of Waterproofing Failure

Our last news article covered the Top 3 causes of waterproofing failure:

  1. Poor workmanship and surface preparation.
  2. The failure to prime the respective parts and surfaces before the application of the waterproofing membrane.
  3. Residual moisture in the substrate causing adhesive failure or de-bonding of the membrane.

This news article informs you of some of the other common causes of waterproofing failure.

  • Film Thickness – incorrect film thickness of the cured waterproofing in the case of liquid applied membranes.  A common problem is the waterproofing has not been applied in accordance with manufacturer’s specifications (e.g. specified number of coats & specified minimum dry film thickness, time required between coats).
    • Waterproofing requires post installation inspection.
  • Product Knowledge – a common failure in waterproofing is the lack of knowledge of the products’ limitations and correct usage.
    • There is no “one can” solution for waterproofing, the product that works well in one situation may fail completely in a different usage.
    • Incompatibility of materials is a widespread problem in the industry which can and does cause failure of the waterproofing.  Multiple products from different manufacturers are not recommended due to the issue of incompatibility.
    • Knowledge of the waterproofing products’ performance characteristics, is a critical part of the serviceability of the waterproofing membrane.
  • Protection of the Membrane – where other Trades are required to work over a waterproofing membrane, temporary protection should always be installed.
    • In the case of Tilers installing tiles by “direct stick”, working on the membrane is inevitable.  However, the membrane characteristics for shore hardness should be considered to prevent damage.
  • Effective Curing – an often ignored problem is the required time for effective curing of liquid applied waterproofing products.  In many instances the waterproofing is installed one day and the next day screeds and tiles are installed over partially cured membranes.
    • Drying and cure times for liquid applied waterproofing membranes are dependent on ambient relative humidity, ambient temperature, porosity of substrates, air flow and substrate temperature.
    • Most membrane manufacturers specify minimum cure times.  These average from 24 to 72 hours.  Note: Wet-seal’s membrane cure time requirement is to allow an adequate drying time of 48 hours at 25 0C and 50% relative humidity.
    • With solvent based and liquid applied membranes, incomplete curing will adversely affect the polymeric properties of the material causing failure.
    • Good building practices require due process and appropriate times for drying and curing of waterproofing, the same as any other material.
    • A Builder would not have the painter paint wet plaster, so why install tiles on uncured waterproofing membranes?

For any other advice of a technical nature, Wet-seal’s highly experienced technical expert, Robert Rath, will be happy to take your call.  Robert can be contacted on 0800 436 000 or via email rrath@wet-seal.ws

Alternatively, please speak with your local Franchisee directly.  Details of how to contact your local Franchisee can be found at Find A Franchisee