More than a decade of masonry works unselfishly provided our company time to research through first-hand experience about efflorescent culprit.
Few times, in the younger years of our company works, some client reached out to us after a month or so pointing their fingers on us because a fine, white, powdery deposit appeared in their walls (stones or bricks). That salt like deposit is efflorescence.
According to the Masonry Institute of America (nd), Efflorescence is the stubborn problem that has caused confusion and trouble for masonry since the first time it appeared thousands of years ago on ancient masonry walls. Efflorescence is normally the white, powdery scum that can appear on masonry walls after construction but can also be brown, green or yellow, depending on the type of salts. Nobody likes it, nobody wants it on their walls, but occasionally this persistent problem appears.
We conducted on site experiments trying every strategy to eliminate possibilities of efflorescence. Patience, great deals of time, money and effort have been spent trying to solve the difficulties caused efflorescence. In fact, many test programs have been developed and numerous attempts have been made to eliminate the efflorescence problem. Unfortunately, nothing has proven 100% effective against this very stubborn problem. However, even though no surefire cure has been discovered, a great deal has been learned about how efflorescence works and how to prevent it, and if preventive measures are inadequate, how to remove the efflorescence if it does appear.
Three Phenomena for Efflorescence Existence:
- Water-soluble salts must be present somewhere in the wall.
- Sufficient moisture in the wall exists to render salt into a soluble solution.
- There is a path for the soluble salts to migrate through to the surface where the moisture can evaporate, thus depositing the salts which then crystallize and cause efflorescence.
The good news is, if any of these three is not present, efflorescence cannot occur. More than that, even though efflorescence problem is complex, IT IS NOT DIFFICULT TO PREVENT!
Then, Who’s the culprit?
The Masonry Institute of America shared findings of their research. According to the, A chemical analysis of efflorescent salts in the Southern California area reveals that they are principally alkalies of Sodium Sulfates (Na3S04) and Potassium Sulfates (K2S04).
These are the main soluble salts to be concerned with in Southern California since these are 90% of the efflorescence found in this area. These alkali sulfates appear because they exist somewhere within the masonry wall, either in the brick, the mortar, or the grout, or possibly a combination of these three. These alkalies combine with sulfates from the masonry to form sulfate salts. The alkali sulfates in the wall are dissolved by water into a solution which then moves through the natural pores in the masonry. The solution migrates to the surface of the wall where the water evaporates, depositing the salts on the wall and generating the white powdery scum we know as
Research into each of the materials used in masonry walls reveals that the main source of alkalies for the salts is the cements used in the mortar and grout. Using a low alkali Portland cement will often eliminate the efflorescent problem. It is recommended that low alkali Portland cement be used to reduce the chances of efflorescence occurring. Low alkali Portland cement has 0.6% alkali or less, by weight in the cement ,
Another culprit is, of course, the clay brick itself. The natural clays used in the manufacture of brick often contain soluble alkali sulfates. Most modern fired clay brick have balanced chemical additives, such as Barium Carbonate (BaCO3), to immobilize the sulfates and render them insoluble. This prevents the salts from being dissolved into a solution that could migrate through the wall to the surface. Most fired clay brick do not greatly contribute towards the efflorescence problem.
The next source for soluble salts would be the sand used in the mortar and grout. Contaminated sands with soluble alkali sulfates will cause efflorescence unless the sulfates are removed. Using clean, washed sand will eliminate any efflorescing contribution.
The water used in the mortar and grout during construction can also be a source of contaminants. Clean, potable, salt free water must be used at all times. Tests of Colorado River tap water show only insignificant amounts of salts in the water. Water from other sources should be checked for their alkali sulfate contents to be sure no efflorescing salts will be introduced into the masonry wall.
Potential efflorescent problems can be greatly reduced by using low alkali cements, clean washed sands and clean, potable salt free water.
In conclusion, three phenomena must exist before efflorescence can occur. If these three conditions can be controlled, there should be no efflorescing of masonry walls.
Hence, our company has been observing strategies and practicing techniques in order to prevent efflorescence. To mention a few of our best practices, we make sure to: Reduce all soluble alkali sulfates; Utilize good details to prevent water from entering the masonry; and we maintain high standard of construction practices to eliminate migratory paths for moisture.
We keep it inculcated in our mind that it is very difficult to totally control any one of these three conditions, but it is relatively simple to reduce the effect each one has towards efflorescence. So far, our company has eliminated calls from past clients having efflorescence problems. A success indicator indeed! Hence, we are not part of the culprit!
Investigation of the Source of Efflorescence of Brick Masonry, Donald W . Bolme and Lester P . Berriman, Stanford Research
Institute, Clay Products Promotional Fund, 1960.
The Causes and Control of Efflorescence on Brickwork, Wayne E. Brownell, Structural Clay Products Institute, 1969.
Investigation of Methods for Reducing Efflorescence of Masonry, James M. Ross and Lester P. Berriman, Stanford Research
Institute, Clay Products Promotional Fund, 1961.
Fundamental Factors Influencing Efflorescence of Clay Products, W. E. Brownell, The Journal of The American Ceramic Society,
Can Efflorescence be Controlled?, Jeffrey Elder, Brick Architecture and Landscape, Summer, 1995
Masonry Institute of America (nd) Retrieved from https://www.masonryinstitute.org/pdf/612.pdf . June 2022