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Posted at: Nov 2, 2019, 9:23 AM; last updated: Nov 2, 2019, 9:23 AM (IST)

Check that ‘shora’ on your walls

Efflorescence in a building can play havoc with the masonary walls. Here are tips to protect the buildings from the crystalline salt deposits that can ruin your walls
Check that ‘shora’ on your walls

Raj Kumar Aggarwal

Efflorescence is a crystalline, salty deposit that appears on the surface of brick walls (also known as kallar or shora local names). Whereas rise of the ground water in walls is termed as dampness. Efflorescence in buildings is a serious problem and plays havoc with masonary walls. If proper care is not taken during or after the construction and due to use of poor quality of bricks and water the building becomes inhabitable and unhygienic after some time. The use of saltish water during construction and through rains, the salts (like sulphates or magnesium, sodium, calcium and calcium carbonate) present in the body of wall get dissolved. This absorbed water on evaporation from the exposed surface of the brick wall causes the salts as deposits on surface of the wall in concentrated patches, either as white powder or as translucent crystals. This results in serious disfigurement on inner and outer faces of walls. 

Another cause of efflorescence is pyrites in clay or in soils, the source of sulphur dioxide, which contribute efflorescence in the form of sulphate salts. All these salts react with certain compounds of cement causing the weakening, cracking and crumbling of cement mortar and wall plaster of buildings.

Attempts to seal back efflorescence are not usually successful and it is advisable to allow the efflorescence to expand itself fully before applying any treatment for its removal. Small efflorescence can be removed with a brush and water. Remove it from the wall surface by scrubbing efflorescence as much as possible. Heavy deposits of exterior efflorescence in existing buildings can be removed to a great extent by firstly washing the wall with clean and salt freewater and then treating with dilute solution of one part of hydrochloric acid with 25 parts of water followed by again washing with water and finally brushing surface efflorescence when wall gets dry.

You can also use zinc sulphate, sulphuric acid, acetic acid (5 per cent white vinegar), citric acid (lemon) or baking soda in place of diluted hydrochloric acid to remove the efflorescence. Remember that several mild applications are better than one over-powering dose. It can also be checked by repeated washing of walls with clean potable or canal water and then brushing the efflorescence from the surface of the walls.

Building owners doing reinforced brick roofing or jack arch roofing generally come with complaints of appearance of some white patches on the ceilings of their buildings. The bricks used in the roof contain a type of lime which causes white patches (lime efflorescence). Best way to avoid this is to use reinforced cement concrete (RCC) roofing instead of reinforced brick roofing.

Interior efflorescence can be checked partially by first allowing it to develop fully, and then removing the same with a stiff wire brush or to reverse the evaporation gradient initially, so that evaporation takes place from the exterior surface of the wall. This reversal can be attained by applying suitable colourless water proofer/epoxy-based coating to the interiors to stop evaporation from the inner face for better results. In chronic cases, ugly patches of efflorescence and dampness can be consealed by lining the walls with non-corrugated asbestos cement sheetes or PVC sheet panelling that is easily available in the market on reasonable prices.

How to test it

Water, sand and bricks should be tested for its salt contents causing efflorescence before using in construction of buildings. For finding out the presence of efflorescence in bricks, out of the stack of bricks, select five bricks at random. All these  bricks should be immersed on end in a shallow dish containing one inch deep clean distilled/potable water. The bricks should be allowed to stand in this position in a warm and well-ventilated room until  the water in the dish is evaporated. The same process should be repeated for the second time also on the same bricks. At the end of second process, the bricks are visually examined for efflorescence. The first class bricks shall not show any appreciable sign of efflorescence (whitish deposits) on its surface after the second process. Bricks containing efflorescence should be avoided in construction of buildings. Efflorescence can also be checked by use of concrete hollow bricks as the hollow bricks do not contain lime. Their thermal insulation properties also reduces the energy consumption of cooling and heating devices. These also provide more sound insulation as compared to bricks.

Prevent entry of moisture

Efflorescence is also directly linked with moisture. Prevent the entry of moisture from walls by using impervious coping on top of walls and parapets, sealing of all joints, providing adequate drips on all copings, projections and cornices. Most importantly, by using efflorescence-free bricks and salt-free water or treated water. Provide damp-proof course, 9” above the ground level in all walls during the construction, so that wall may not get saturated with moisture carrying the soluble salts from soils. By using clean and potable or canal water free from suspended material, organic impurities, acids, alkalies and salts for the construction and for curing work, we can have a newly constructed buildings free from efflorescence and related problems.

— The writer is executive engineer, Baba Farid University of Health Sciences, Faridkot


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