Efflorescence, Can it be Controlled? An information Paper from Western States Clay Products Association By Jeffrey L. Elder, S.E., LEED AP

Introduction most basic concept of The absence of any one of these The masonry industry has long efflorescence occurs when three elements will virtually been plagued with concern and water reacts or mixes with eliminate efflorescence. confusion for what has been masonry materials to move salts termed efflorescence. to the surface of the element. In Salts some cases, the water reacts Water-soluble and non-water- Although efflorescence is not with the masonry components soluble salts may be present in well understood, the masonry to create free salts. the masonry units, industry is able to generally ingredients (cement, lime, , define what it is, where it comes admixtures and other from, and how to reduce the constituents), grout ingredients potential of it occurring. (cement, sand, aggregates, and other admixtures), water, Definition contacting soils, and windborne Efflorescence is a deposit of chemicals and dusts. soluble salts which usually appears as a fine, white, Some soluble salts in masonry crystalline powder on the are created as a result of the surface of masonry as the reaction between masonry units, internal water evaporates. If In other instances, free water mortars, grouts, embedded the salts are non-soluble (they dilutes already-free salts in the conduits and reinforcing. It is don’t break down in water), masonry into solution which not until the masonry element is they are not considered can be transported through the constructed that the salts efflorescing salts. masonry element. If the salt become soluble. deposits are transported to the surface, we refer to them as efflorescence.

If the salts are deposited within the masonry where they form a crystal, we refer to the salt deposit as crytoflorescence. Since these are not visible, their presence is often discovered after the crystal formation Efflorescence sometimes appears as a brown, a green, or creates forces in the masonry sufficient to cause spalling. If the masonry element is a yellow stain resulting from the exposed to large concentrations presence of different types of In order for efflorescence to of moisture such as rain or snow salts. during construction, but prior to occur, a masonry must contain soluble salts, water, and hydration, setting and bonding Causes of the mortar and grout, the Efflorescence is a very complex a force to move the -dissolved salts to the exterior of the wall. salts in the materials are more problem to understand. The susceptible to being dissolved. Cleaning solutions may also can dissolve salts in the Regions of high humidity will react with masonry materials to masonry materials. Dissolved also be exposed to greater create soluble salts. Cleaning salts are carried to the surface efflorescence potential. In these agents high in acid content are by forces of evaporation. regions the author recommends the most notorious for bringing conducting a wick test on the out efflorescence as they are Although clay are the only entire masonry assembly or quick to dissolve most salts. products required to be tested prism.

In order to dissolve a salt, there needs to be sufficient solution. Water is the solution. The more water available, the more salt is able to be dissolved.

Masonry Unit The absorption and porosity of the masonry unit may also have an impact that may not be recognized until after the wall is constructed.

For instance, the author has Certain water-soluble salts according to ASTM C67, the observed that certain masonry present in the masonry units, author recommends testing the units classified as “not mortars, and grouts can be other constituents for their effloresced” according to determined prior to installation contribution to efflorescence. ASTM C67 effloresce more in by testing the components using Mortars and grouts can be the wall than other units the wick method outlined in major contributors to designated as “effloresced”. ASTM C67. efflorescence and should be In some cases these “not In this method, the masonry unit tested. effloresced” units are darker is placed in a tray of distilled which make efflorescence stand water for 7 days. Distilled water The designer should recognize out more than on light colored is selected because it is salt free that specifying “not units. and eliminates the water as a effloresced” brick is not a sure potential source of salt. During remedy that efflorescence will the test, water is wicked through not occur on their project, only the masonry element where it that the materials are not the contributor.

Moisture The potential of a masonry element to effloresce is directly related to its exposure to moisture. Masonry construction in coastal and other high annual Some “not effloresced” brick rainfall regions will be exposed have higher absorptions. The to higher quantities of water higher absorption brick allow more water to enter the masonry both during and after construction. which provides more water to

2 dissolve and transport free salts boulders are frequently moved The north and east facing in the wall. A prism wick test in the Colorado. are normally cooler; might bear this out. consequently, water within the Efflorescing salts are large wall is allowed to move to the Temperature particles in a wall and require surface before it evaporates. On The exposure of a masonry higher flow rates to get them to these faces, the salts would be element to temperature also has move through the wall. Lower transported to the surface and an impact on efflorescence. temperatures reduce the flow of would exhibit more Temperature has two effects on moisture and consequently have efflorescence. the masonry. The first is speed little impact on the salts. of water movement in the wall Removal and the second is location of In understanding efflorescence, If efflorescence does appear, the evaporation. it is also important to consider safest approach is to assume that salt formation occurs at the that the salts are water soluble. As the temperature of the air margin between saturation and If this is the case, the salts can and the masonry increases, this evaporation. Consider the south easily be removed using a dry increases evaporation. face of a building or the top of a brush, rinsing with water, or paving brick. As the face of the through natural weathering brick gets warm it causes processes. evaporation to occur on the surface. As the surface of the brick begins to dry, it moves the point of saturation deeper into the wall. It is at this location that salts are deposited.

The formation of salt crystals in The rate of evaporation has a a masonry element is referred to significant impact on movement as crytoflorescence. If the salt of salts in a wall. This can be concentrations beneath the understood conceptually by surface of the brick create contrasting the Mississippi If the salts are not water forces in the clay that exceed River with the Colorado River soluble, attempt to identify the the material tensile strength, at flood stage. The maximum type of salts present. Consult one might observe spalling. It is particle size of transported the masonry manufacture for the author’s belief that it is the materials in the Mississippi is assistance in identifying free formation of these crystals in limited to fine silts and . salts. Vanadium and pavers that causes spalling more On the other hand, house sized Manganese are salts inherent in often than water freezing. many buff and brown and black colored brick. These and other It is for this reason that south salts may require special and west facing walls are less cleaning agents to remove them. prone to efflorescence. These . walls receive more exposure to Other salts dissolved from the the sun and become hotter. As masonry react with the air once these walls become warmer, the they reach the surface. These location of evaporation moves salts combine to form non- further into the wall. soluble salts and are difficult to remove with standard cleaning

3 methods. Some of these salts breathable water proofing form the actual job site units, require sandblasting or staining materials. These act as a barrier mortars and grouts and then to remove or mask the salts. to large particles and may subjecting them to the ASTM Common sources of these types increase crytoflorescence and C67, wick test. of salts come from soils and spalling. sprinkler type irrigation. Stockpile masonry materials on Material Selection pallets above the ground. Prevention Masonry materials should be Wicking of salts from the All masonry elements are selected which have the least ground is a common problem. susceptible to efflorescence source of salts. Select since all masonry contains free cementicious materials which Detailing salts and are exposed to pass ASTM specifications. The architect should select moisture. details which are less Where available, use low alkali susceptible to effloresce. Avoid cements. High alkali cement horizontal masonry copings in are known source of wet climates. Specify mortars efflorescing salts. Avoid sands with proven resistance to that have not been washed or efflorescence. Call out mortar which have been exposed to joints as tooled concave or V- contaminants. Avoid masonry joint in climates exposed to units that are known to high rain or freezing. This will effloresce in the stockpile. Use help to reduce the water clean, potable water free of permeance of the mortar. acids, alkalis and salts. Select caulking and sealant Test masonry assemblages for materials compatible with the efflorescence and select masonry and other adjoining combinations low in materials. Provide flashings efflorescence. and weeps in masonry walls at locations where water can High vapor transmission rate accumulate. Provide weep (VTR) water repellents have holes and air vents wherever been known to help in reducing possible. Vents allow for efflorescence by reducing the evaporation to occur on the amount of water that gets into a inside of a wall which helps to wall thereby reducing the keep the salts suspended in the amount of solution available to wall. The author does not dissolve the salt. Water recommend cotton wicks repellents also help in reducing because of their inability to the rate of evaporation which move water. slows down the flow of water in the wall which reduces the Use wide overhangs and rain transportation of larger gutters where architecturally particles. feasible. A continuous damp proofing membrane should be High VTR water repellents Much could be learned to applied at the base of the wall allow the salts to migrate to the minimize efflorescence by above the soil line to prohibit surface. Stay away from non constructing masonry prisms

4 salts in the soil from rising into Follow recommended construction of a masonry the masonry. construction practices in hot and element will reduce cold weather climate. Cleaning efflorescence. Masonry used to contain soil masonry requires the masonry such as in planters and retaining units to be saturated before Reference walls allow wicking of salts applying masonry cleaners. 1. Chin, Ian R. and Lee Petry, from the soil through the This is to prevent cleaning “Design and Testing to Reduce masonry onto the face of the solvents from being absorbed Efflorescence Potential in New masonry wall. Since these salts into the brick where they can Brick Masonry Walls.” ASTM are normally not water soluble, breakdown efflorescing salts. STP 1180, Philadelphia, 1993 damp proofing should be placed 2. “Control and Removal of between the masonry and the Water repellents should be Efflorescence”, TEK 92, soil to stop salt migration. applied to masonry during National Masonry warm weather so that they can Association, 1993. Landscape, sprinkling systems, be absorbed more deeply into and downspouts should be the brick. 3. “Efflorescence”, CSI properly placed to avoid splash monograph, Feb. 1987. back. Consider the use of water Conclusion repellents carefully and their Almost all masonry components 4. “Efflorescence, Causes and effect on durability. contain soluble salts and Mechanisms”, Technical Notes additional salts may be formed 23 revised, Brick Institute of America, May 1985. Masonry used as a paving unit as the masonry components are should be designed with combined. 5. “Efflorescence, Prevention adequate drainage and isolated and Control”, Technical Notes from soil where possible to When sufficient water is added 23 A Revised, Brick Institute minimize contact with salts in to the masonry element prior to, of America, June 1985. the soil. Avoid applying de- during, or after construction, the icing salts to paving areas. De- salts dissolve and go into 6. Grimmer, Anne #., “Cleaning icing salts will cause solution form. When these Efflorescence from Stone efflorescence and may cause move to the surface, the result is Surfaces”, Stone World, July spalling. efflorescence. To reduce 1994. efflorescence, the selection of 7. Koski, John A., “Removing Construction materials with the least potential Efflorescence”, The Magazine Proper construction is critical in for efflorescence should be of Masonry Construction, May establishing a moisture resistant considered. 1992. wall and a wall less susceptible to efflorescence. One way to evaluate the 8. Matthys, John H., masonry assembly’s “Conventional Masonry Protect partially completed efflorescence potential is by Mortar Investigation”, masonry from moisture during conducting a wick test. Careful University of Texas at construction. Moisture allowed attention should also be made to Arlington, National Lime into a masonry element during prescribe details and Association, Arlington, VA, construction can be the greatest construction practices that will 1988. source of efflorescence. Open reduce the elements exposure to cells containing water should moisture. 9. Merigan, Michael W., not be grouted. “Efflorescence: Cause and A thoughtful approach to the Control”, Masonry Institute selection, design and of America, Jan 1986.

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