Efflorescence and its Treatment in Concrete and Brick Masonry
Efflorescence, the deposit of water-soluble salts on the surface of concrete and brick masonry, can be a common issue in construction.
It occurs when water carrying dissolved salts moves through the pores of the material and evaporates, leaving the salts behind. In this article, we will explore the causes of efflorescence and discuss various treatment methods to effectively combat this problem in concrete and brick masonry.
A. Causes of Efflorescence:
Efflorescence formation requires specific conditions to be met. The following factors contribute to its occurrence:
1. Presence of Soluble Salts:
Concrete and brick masonry walls should contain soluble salts, which can originate from masonry bricks, mortar, adjacent soil, or backing materials.
2. Water Contact:
Water must be present in the concrete or brick masonry walls and come into contact with the soluble salts, dissolving them.
3. Pore Structure:
The concrete or brick masonry walls should possess a pore structure that allows the migration of soluble salts to the surface, where water can evaporate, leaving behind the salt deposits.
B. Efflorescence Treatment on Concrete and Masonry Surfaces:
To effectively treat efflorescence, various methods can be adopted, focusing on material selection, design and detailing, and construction practices.
1. Material Selection:
Choosing materials with a low potential for efflorescence is crucial. For example, cement with low alkali content should be preferred, as higher alkali content increases the likelihood of efflorescence formation. Additionally, using potable water and clean, washed sand in grout or mortar mixtures is recommended. Building trims, such as copings and sills, should also be made from low salt content materials. Material testing can be conducted to determine their potential to cause efflorescence.
2. Design and Detailing:
Proper design and detailing can help minimize or eliminate water penetration, reducing the chances of efflorescence formation. Recommendations include:
Watertight Below-Grade Masonry:
Groundwater often contains significant amounts of soluble salts, which can accumulate in masonry and lead to efflorescence. Employing watertight masonry below-grade and installing base flashing to redirect water away from the wall can help mitigate this issue. Additionally, using grout or mortar to support base flashing below the air space is advisable.
3. Construction Practices:
Implementing good construction practices is essential in reducing efflorescence formation. The following practices are recommended:
Utilize Clean Water:
Using clean water free from salts during construction is important to prevent introducing additional salts into the masonry.
Properly storing masonry units and protecting them from dirt, contamination, groundwater, snow, and rainwater during transportation and construction is crucial.
Adequate Joint Filling:
Ensuring sufficient filling of joints, such as mortar joints in solid unit masonry or face shells in hollow unit masonry, helps establish a strong bond between the units and prevents the ingress of wind-driven water.
Covering Unfinished Brickwork:
Covering partially completed masonry work with waterproofing membranes at the end of each working day is recommended. This prevents rainwater from saturating the masonry, reducing the likelihood of efflorescence formation.
C. Removal of Efflorescence:
Efflorescence can be removed using various methods, depending on the specific situation. The following approaches are commonly used:
1. Dry Brushing:
If the salt deposits are soluble, dry brushing can be an effective way to remove them.
Rinsing the affected area with water or other suitable liquids can help eliminate efflorescence.
3. Hand Washing:
For smaller efflorescence patches, hand washing can be an appropriate method.
In more severe cases, sandblasting can be employed to remove efflorescence.
5. Special Chemical Cleaners:
There are specialized chemical cleaners available that are designed specifically for efflorescence removal.
6. Ordinary Chemical Cleaners:
In some instances, ordinary chemical cleaners such as muriatic acid may be used, but caution must be exercised to avoid any damage to the surface.
It’s important to note that efflorescence removal and cleaning alone will not solve the problem. To address the issue permanently, it is necessary to seal the wall effectively.
Efflorescence can be a frustrating problem in concrete and brick masonry, but understanding its causes and implementing the appropriate treatment methods can help prevent and address this issue. By carefully selecting materials, employing proper design and detailing, and following good construction practices, efflorescence can be minimized.
In cases where efflorescence does occur, the appropriate removal methods should be chosen, keeping in mind the solubility of the salts and the specific situation. By combining these efforts, we can ensure long-lasting, aesthetically pleasing concrete and brick masonry structures free from the burden of efflorescence.