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Efflorescence is the term used to describe crystalline (or
powdery) deposits, usually white in colour, that sometimes form on the
surface of brickwork, concrete plasters and other concrete type structures.
In most cases efflorescence is the result of calcium hydroxide (lime)
from cementitious substrates being carried to the surface by water.
This then reacts with carbon dioxide in the air to form insoluble calcium
carbonate. Normally efflorescence is only of cosmetic concern although
it can ruin the appearance and physically damage paint coatings.
Efflorescence is most often the result of uncontrolled moisture movement
caused initially by poor design details and poor construction techniques.
Before attempting to remove efflorescence the source of moisture getting
into the substrate should be eliminated.
Ensure:
- Joints and cavities are properly sealed;
- Rainwater run-off is diverted to suitable drainage;
- Physical barriers are in place between brickwork and in situ concrete;
- Tops of parapets have cappings and windows and doors have suitable
flashings in place;
- Cavities are well-ventilated;
- Vapour barriers are used to stop uptake of groundwater.
Efflorescence can be removed by physically scrubbing with a stiff brush
and careful washing. Waterblasting may result in a continuation of the
efflorescence as more water may be blasted into the substrate. |