Mastercivilengineer

Efflorescence is a deposit of water-soluble salts formed on the surface of brick masonry and concrete due to the movement of water through pores. When water gets evaporated, efflorescence is formed as the dissolved salt gets deposited on the surface.

Causes of Efflorescence  

The condition in which efflorescence occurs is unique and all conditions should be met otherwise brick masonry and concrete would not suffer from it.

There are three main conditions that offer excellent conditions for efflorescence formation on brick masonry walls and concrete. These conditions are as follows:

• Brick masonry wall should contain soluble salts and the salt might be in masonry brick, mortar, adjacent soil, and backing material.
• Water should present in the brick masonry wall and need to be in contact with soluble salt to dissolve it.
• Brick masonry wall shall possess a pore structure to permit the migration of soluble salt to the surface where water may evaporate and leave the salt.

Efflorescence in Bricks

Usually, sulfate of magnesium, calcium, carbonate, and sulfate and sometimes chloride and nitrates of sodium and potassium are found in efflorescence. These salts may be traced to the brick itself and used in construction work, the foundation soil, groundwater, water used in the construction work, and loose earth leftover in contact with brickwork. Bricks with magnesium sulfate content higher than 0.05% should not be used in construction. The soluble salt content in the sand should not exceed 0.1%.

Water, if it finds access to brickwork, moves along its pores by capillary action and carries with it dissolved salts. As the solution evaporates from the exposed surface of the brickwork, the salts are lest as a deposit on the surface on the layer just below it. Disintegration or flaking of the brick surface is caused by the mechanical force exerted by slats as these crystallize just below the exposed surface. Magnesium sulfate, in particular, disintegrates bricks and pushes out a plaster.

Remedies

• Well fired brick should be used in construction work.
• Sand should be tested for its salt content at the construction site.
• Proper D.P.C (Damp Proof Course) should be provided in the building.
• Efflorescence in brickwork traceable to salts in the material can be removed by brushing and washing repeatedly. Such efflorescence may re-appear in the dry season but usually are less in intensity. The finally these disappear as the salt content of the brick is gradually leached out.

Efflorescence Treatment on Masonry and Concrete Surface  

Following methods can be adopted for treatment of efflorescence.

• Material Selection
• Design and Detailing
• Construction Practices

Material Selection

Avoid the selection of materials that have low potential to produce efflorescence. For example, use cement 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 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.

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 contributes to the prevention of efflorescence formation.

The design measures that recommended avoiding efflorescence formation involve:

Watertight Below Grade Masonry

Commonly, groundwater contains a 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 installing 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.

Flashing on Trim 

Flashings shall be employed to prevent capillary action and avoid contact between masonry and trim materials.

Air Space  

Air space between the exterior wall and the interior of masonry walls reduces efflorescence formation.

Air space function includes separation of the exterior wall from other elements of a masonry wall, permits water to drain down the back of the brick Wythe, and impede the movement of salts from backing material by separating the brick wythe from the materials containing salt compound.

Proper Detaining 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.

Construction Practices  

Beneficial construction practices that lead to decrease efflorescence formation are as follows:

Utilized Water

Use clean water and free from salts.

Material proportion during transportation and construction process  

The masonry unit shall be isolated from dirt, contamination, groundwater, snow, and rainwater through suitable storing. In addition to cover material during the transportation and construction process.

Filling Joints Adequately

Sufficient filling of joints such as head and bed mortar joints in solid unit masonry, face shell 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 an adequate bond between masonry units and prevent the ingression of wind-driven water into masonry walls.

Covering Unfinished Brickwork

Covering partially completed masonry works with waterproofing membranes at the end of each working day is a must.

If such a measure is not considered, the masonry works may be subjected to rainwater and saturated which takes a 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
• Rising with water or other acceptable liquid
• Hand washing
• Sandblasting
• Utilize a special chemical cleaner
• Ordinary chemical cleaner such as muriatic

There is a number of factors that control the selection of efflorescence removal. For example, if the salt is soluble, it is recommended to apply a dry brush. Hand washing is recommended to choose for small efflorescence batches.

It should be known that the cleaning and removal of the efflorescence on the masonry surface would not solve the problem. So, it is required to seal the wall to tackle the problem permanently.