Efflorescence

In chemistry, efflorescence (which roughly means "the flowering" in French) is the migration of a salt to the surface of a porous material, where it forms a coating.

Since primary efflorescence brings out salts that are not ordinarily part of the cement stone, it is not a structural, but, rather, an aesthetic concern.

[1] Secondary efflorescence is named such as it does not occur as a result of the forming of the cement stone or its accompanying hydration products.

This saline solution is absorbed into the concrete, where it can begin to dissolve cement stone, which is of primary structural importance.

Virtual stalactites can be formed in some cases as a result of dissolved cement stone, hanging off cracks in concrete structures.

For controlling secondary efflorescence, admixtures containing aqueous-based calcium stearate dispersion (CSD) are often added at a later stage of the batching process with the mix water.

[2][3] The only way to completely and permanently prevent (both primary and secondary) efflorescence in cementitious materials is by using special admixtures that chemically react with and bind the salt-based impurities in the concrete when hydrogen (H) is present.

Common rebar protective measures include the use of epoxy coating as well as the use of a slight electrical charge, both of which prevent rusting.

This will reduce efflorescence, spalling and scaling that can occur from water being trapped inside the brick substrate and freezing during cold weather.

Years ago, the water repellents trapped moisture in the masonry wall creating more problems than they solved.