Definition - What does Efflorescence mean?

Efflorescence refers to a whitish, crystaline deposit on the surfaces of masonry, stucco or concrete. Efflorescence is the result of the migration of moisture from within either new or old masonry. When moisture migrates through the wall or floor, it dissolves mineral salts contained in the cement. The resulting mineral salt solution finally moves to the surface of the concrete. At the concrete surface, evaporation of water produces a white deposit of mineral salts, which is known as efflorescence.

Efflorescence is the problem created on the surface of brickwork, concrete plasters and other masonry works.

Corrosionpedia explains Efflorescence

Efflorescence consists of mostly whitish deposits on the masonry surface, resulting from uncontrolled moisture movement through the wall or floor. Most of the time, efflorescence is caused when calcium hydroxide (lime) from cementitious substrates is carried to the surface by water and then reacts with carbon dioxide in the air to form insoluble calcium carbonate. Efflorescence causes physical damage and affects the appearance of coatings.

Three conditions must be met for efflorescence to occur:

  • Water-soluble salts must be present somewhere in the wall
  • Sufficient moisture in the wall is needed
  • A path for the soluble salts to move through to the surface is needed; this will allow moisture to easily evaporate and deposit the salts

Efflorescence comes in two types, based on the curing process:

  • Primary efflorescence – occurs during the curing process. Excess water containing the products evaporates and deposits the calcium hydroxide crystals that are left.
  • Secondary efflorescence – occurs in cured concrete and composites that are in contact with moisture or that are subjected to cycles of re-wetting and drying.

Efflorescence is not the same as laitance.

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