![]() It should be recognized that there must be water (moisture) present to dissolve and/or transport these salts so the source of the moisture needs to be either blocked (if it’s external to the substrate, such as groundwater) or exhausted (if moisture is emanating from within the substrate, such as rising damp). The carbonation process occurs when alkaline salts such as lime (calcium hydroxide) within the pores of the substrate react with atmospheric carbon dioxide to form calcium carbonate that is transported to the surface by moisture.Ĭoncrete or mortar with high levels of Portland cement contains high concentrations of calcium that in turn can often produce excess salts. A reasonable amount of moisture is generally required for the formation of calcium carbonate. Why?Įfflorescence from masonry (concrete, render, brick or plaster) that appears as white alkaline salts on the surface, consists mainly of calcium carbonate. ![]() ![]() The paint film may stretch to form the outline of the growing crystals or the paint film may just rupture, crack, flake or peel instead. Since the mineral salt crystals are not fluid, the pressure is therefore not uniform hence the coating does not form smooth rounded blisters. Paint systems adhering normally to the surface of the substrate can also be forced off (de-laminate), when the pressure caused by the growth of salt crystals builds up beneath the paint film, resulting in its gradual but irreversible destruction. “Efflorescence” is the term most commonly used to describe the deposit of crusty white mineral salts that appear on a masonry surface (concrete, render, brick or mortar) that have leached out from within the substrate when moisture migrates through it.Īny efflorescence on the surface must be removed prior to painting as it is regarded as a poor and friable base that prevents paints and coating systems from adhering effectively.
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