Efflorescence and its Treatment in Concrete and Brick Masonry

Efflorescence is a deposit of water soluble salts formed on the surface of concrete and brick masonry due to movement of water through pores. When water gets evaporated, efflorescence is formed as the dissolved salts gets deposited on the surface.
This article discusses different aspects of efflorescence and its treatment in concrete and brick masonry.

Causes of Efflorescence

The condition in which efflorescence occurs is unique and all conditions should be met otherwise concrete and brick masonry would not suffer from it.
There are three main conditions that offer excellent condition for efflorescence formation on concrete and brick masonry wall. These conditions are as follows:
  1. Concrete and brick masonry wall should contain soluble salts and the salt might be in masonry brick, mortar, adjacent soil and backing material
  2. Water should present in concrete and brick masonry wall and need to be in contact with soluble salt to dissolve it.
  3. Concrete and brick masonry wall shall possess pore structure to permit the migration of soluble salt to the surface where water may evaporate and leave the salt.
Causes of efflorescence
Fig. 1: Causes of efflorescence

Efflorescence Treatment on Concrete and Masonry Surfaces

Following methods can be adopted for treatment of efflorescence:
  1. Material selection
  2. Design and detailing
  3. Construction practices

1. Material Selection

Avoid selection of materials that has low potential to produce efflorescence. For example, use cements with low alkali content since the possibility of efflorescence formation increases with the increase of alkali content.
Moreover, specify potable water and clean and washed sand for the production of grout or mortar mixtures.
Furthermore, building trims for instance copping, sills, and cops that manufactured from low salt content materials shall be selected otherwise the likelihood of efflorescence formation will increase.
Finally, materials can be tested to find out whether they potentially cause efflorescence formation or not for example, test method C 67 efflorescence test for brick.
Efflorescence test on bricks
Fig. 2: Efflorescence test on bricks

2. Design and Detailing

Generally, rainwater can ingress into all kinds of masonry walls to a certain extent, but proper design and detailing can be employed to decline or eliminate the water penetration which subsequently contribute to the prevention of efflorescence formation.
The design measures that recommended to avoid efflorescence formation involves:
2.1 Watertight Below Grade Masonry
Commonly, groundwater contains sizable quantity of soluble salts that may accumulate in masonry and cause efflorescence creation.
This source of efflorescence can be removed through watertight masonry below grade in addition to install base flashing to discharge water out of the wall a few courses of masonry above the grade.
Finally, it is recommended to use grout or mortar to support base flashing below the air space.
Watertight below grade masonry
Fig. 3: Watertight below grade masonry
2.2 Flashing on trim
Flashings shall be employed to prevent capillary action and avoid the contact between masonry and trim materials.
2.3 Air Space
Air space between exterior walls and interior of masonry walls reduces efflorescence formation.
Air space function includes separation of exterior wall from other elements of masonry wall, permits water to drain down the back of the of the brick wythe, and impede the movement of salts from backing material by separating the brick wythe from the materials containing salt compounds.
Air space in masonry wall
Fig. 4: Air space in masonry wall
2.4 Proper Detailing of Movement Joints
If the movement joints are adequately sized, located, and sealed, then water penetration into the wall will be declined to a great extent.

3. Construction Practices

Beneficial construction practices that lead to decrease efflorescence formation are as follows:
3.1 Utilized Water
Use clean water and free from salts.
3.2 Material protection during transportation and construction process
Masonry units shall be isolated from dirt, contamination, groundwater, snow, and rain water through suitable storing. In addition to cover material during transportation and construction process.
3.3 Filling Joints Adequately
Sufficient filling of joints such as head and bed mortar joints in solid unit masonry, face shells head and bed joints in hollow unit masonry, and grapevine mortar joints on the exterior face of the wall is considerably critical factors that must be considered to eliminate efflorescence.
This is will create adequate bond between masonry units and prevent the ingression of wind driven water into masonry walls.
Proper filling of joints reduce water penetration
Fig. 5: Proper filling of joints reduce water penetration
3.4 Covering unfinished brickwork
Covering partially completed masonry works with waterproofing membranes at the end of each working day is a must.
If such measure is not considered, the masonry works may be subjected to rainwater and saturated which takes long time to dry. Consequently, the likelihood of efflorescence formation will increase.

Removal of Efflorescence

The removal of efflorescence is conducted using one of the following methods:
  • Dry brush
  • Rinsing with water or other acceptable liquid
  • Hand washing
  • Sandblasting
  • Utilize special chemical cleaner
  • Ordinary chemical cleaner such as muriatic
There are number of factor that controls the selection of efflorescence removal. For example, if the salt is soluble, it is recommended to apply dry brush. Hand washing is recommended to choose for small efflorescence batches.
It should be known that the removal and cleaning of the efflorescence on masonry surface would not solve the problem. So, it is required to seal the wall to tackle the problem permanently.
Removal of efflorescence
Fig. 6: Removal of efflorescence