Masonry Magazine February 2002 Page. 32
EFFLORESCENCE/continued
HOW DID THE SALTS GET THERE?
It has often been stated that there are three components necessary to create efflorescence: soluble salts, water to dissolve salt, and force to move solution to the surface of the wall. Elimination of any one of these three will most likely eliminate efflorescence on the surface of masonry.
In the beginning, quantities of a "salt-like material" are dissolved in water. Then the water is drawn to the surface through some pathway, such as cracks in unit masonry, cracks in mortar joints, or by passing through a more porous material. In the spring, the catalyst for drawing the water to the surface is the warming air on the exterior. Once the water reaches the surface, the water evaporates and deposits the salt like material on the surface.
The most common source of salt is the water used in mixing mortar or cleaning masonry. The specifications usually call for water, which is potable, that is to say drinkable.
Sand used in mortar is another common source of salts. Sand should be washed with fresh water. Spring and well water, as well as seawater, could contain salts. Often the sand is stored on the ground and picks up ground water.
Manufacturers of masonry units go to great extremes to minimize the salts found in the units. There are a number of tests, which can be run, to show whether salts are present or not. However, since the main source of salt is the earth, there are still some brick, which may contain salt. Manufacturers have methods and additives, which can be used to minimize salts. Since this is the smallest source, we will not address that topic here.
HOW TO AVOID IT
To avoid efflorescence, several precautions should be taken during construction. All materials should be stored off the ground to assure that ground water does not contaminate the materials. This means brick and block should be stored under cover on pallets. Tops of walls should be covered at all times during construction to prevent unnecessary water build-up in cavity. The use of silos or blended mortar material probably may prove to be the best solution for protecting sand, cement and lime on the jobsite.
When cleaning masonry, on the other hand, a large amount of water is necessary to flush cleaning products and excess mortar from walls. This introduces water back into the system, so the water used here is critical. It must be clear, potable, and salt free.
EFFLORESCENCE IN OLDER BUILDINGS
A sign of a need for maintenance in an older building is efflorescence. This could be a sign of needed roofing repairs, gutter and downspout repairs, flashing failure, or even just caulking failure. These repairs should be made and wall systems should be allowed to dry before attempting to clean stains.
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