It can be said that today the main cause of efflorescence in the masonry of ceramic blocks or of concrete It is also the free Calcium Hydroxide or Magnesium Hydroxide (also called Free Lime) present in the settlement mortars and lateral coiling.
Because these are places with a greater presence of cement, the spots of rods and cross bars, and also the spots of channels in general, efflorescence may occur more frequently. This happens because when rains occur, water flows down inside the blocks, dissolving “Free Lime”, which accumulates at these points, which act as horizontal bulkheads.
Free lime is a mixture of calcium hydroxide and magnesium hydroxide that react with atmospheric carbon dioxide according to the reactions below:
The cure of Free Lime is a carbonation reaction, which generates an increase in molecular weight and, consequently, an increase in volume.
For the built environment to be preserved, it is necessary to block the passage of moisture, whether this water comes from rain or from pools, washes or other agents that cause the dissolution of Free Lime.
This blockage can be done, to name a few examples, by plastering the external walls with mortar in accordance with technical standards (industrialized or built on site), covering the property, waterproofing the washable areas, applying silane-siloxane-based water repellants from the outside, such as BlokSeal of Souza Filho Waterproofing.
Perform coating of plaster on top of a brickwork with efflorescence will cause pathologies such as dislocation, staining, bursting, loss of mechanical strength, “popping” (when the coating of plaster it seems to be foaming), lack of anchorage for painting, and others.
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To combat efflorescence, Souza Filho Waterproofing It developed Blok Eflohard. This product converts efflorescence into hard crystals, avoiding harmful aspects.
The application is very simple. Simply wipe the surface with a clean damp cloth and apply two coats with an interval of one hour between them.
To prevent efflorescence on the brickwork, care must be taken to ensure that water does not penetrate and thus does not cause moisture to the surface.
Only water can dissolve free salts, which are mainly present in the cement that makes up the mortars.
Some semi-ready (pre-dosed), bagged, ensiled, or stabilized mortars (already sold with the addition of water), in many cases, use air removers in their formulations, which are surfactants, which may lead to an increase in the solubility of certain salts present mainly in mortar cements, thus leading to a greater occurrence of efflorescence.
If the mortars contain hydrated lime, the efflorescences will be larger.
If CP III cement is used, these efflorescences will be lower. Cements with a higher fineness modulus (finer cements) tend to be more impermeable cements, therefore, with a lower tendency to form efflorescence.
The efflorescence that causes the greatest degradation in ceramic blocks is that due to the migration of free lime, as it will expand during the curing process, leading to delamination (gradual loss of wall of the blocks).
Therefore, in order to avoid the formation of efflorescence, appropriate precautions must be taken to prevent the passage of water, whether through the facades, internal walls of the built environment and underpinning.
Until the passage of moisture ceases, the appearance of efflorescence will remain, and if these affected sites are not treated with the appropriate efflorescence converter, new pathologies will arise.
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