WHAT IS EFFLORESCENCE?
Efflorescence is a crystalline deposit that forms on masonry, stucco or concrete surfaces. It has been studied and reports were written as early as the late 1800’s. The formations of these salts are always whitish in appear¬ance. They are, for the most part, water-soluble salts that come from many possible sources and detract from an other¬wise beautiful and serviceable structure. First of all, there must be water present to dissolve and trans¬port the salts to the surface. Groundwater and rain water are most often the source of efflorescence. For the salts to come to the surface there must be channels through which the water can move and migrate.
The more dense the material, whether it be brick, stone, stucco or concrete, the more difficult it is for the water to transport salts to the surface. Conversely, the more porous the material, the easier the salts are transported and deposited on the surface. Salt-bearing water, on reaching the surface of a structure evaporates into the air and leaves the salt deposit. In areas of low humidity, the water may evaporate before reaching the surface, leaving the salt deposit beneath the surface, and unseen. Since humidity and rain have a definite effect on whether or not the salts appear, it can be assumed that efflores¬cence is a seasonal problem. The intensity of efflorescence increases during the rainy seasons, de¬creases in spring, and by summer has practically disappeared. This cycle may repeat for months or years, but generally the intensity of the efflorescence decreases in all but very extreme cases, is practically eliminated in about three years. Sand and gravel, in their natural state, are associated with salt being a part of the mixture used in these substrates.. If these salts are not removed by washing, this is the most likely source of the efflores¬cence. Another potential source of soluble salts is clay products, such as building brick and face brick. Building brick must be stored in a dry place off the ground to prevent absorption of moisture or damp¬ness from possible salt bearing soil. It has also been noted that the occurrence of efflorescence bears a relationship to the type of mortar used. With a particular type of brick and a certain mortar no efflorescence may occur, whereas, the same brick with different mortar may produce a wall heavily coated with salt deposits. Since, for the most part, concrete masonry is somewhat porous, evaporation of the salt bearing water usually takes place before reaching the surface when exposed to the atmosphere.
How can we remove Efflorescence?
There are several ways to remove Efflorescence.
1. Use a pressure washer at about 2,500-3,000 psi.
2. Brush the surface thoroughly with a stiff brush.
3. Use muriatic acid and water solution with subse¬quent flushing with water. Acid applied to brick masonry, without previous wetting, may cause "burning" or discoloration of the brick and may also eat into the mortar. A test area should always be done prior to taking on the whole project. The recommended acid mixture is one (1) parts hydrochloric to twenty (20) parts water, or one (1) part white vinegar to five (5) parts water. 4. Light sandblasting may be used for removal of stubborn efflorescence that has been present for several months or more. Care should be taken in applying acid to Portland cement based products. The acid will attack, not only the calcium carbonate and calcium sulfate efflorescence, but also other calcium compounds to produce calcium salts such as calcium chloride. It is, therefore, very important to neutralize the acid before it can attack other compounds. It can be neutralized with a solution of ammonia and water or baking soda and water.