Ever noticed a sudden white, powdery deposit on the surface of your wall, brick, ceiling, or concrete structure and wondered, “Where did this white substance come from?” This white deposit is known as efflorescence.
What is Efflorescence? – Efflorescence Meaning
The word efflorescence means “to flower out.” In construction, it refers to salts that “flower out” from masonry surfaces. It is one of the most common problems faced by contractors, especially in colored concrete and brick structures.
Efflorescence is a crystalline salt deposit that forms on the surface of concrete, brick, stone, or walls. The presence of water is essential for its formation. When water containing soluble salts migrates to the surface and evaporates, it leaves behind white or greyish salt deposits.
Although efflorescence initially appears to be an aesthetic problem, prolonged moisture movement can lead to durability concerns and gradual material deterioration. Therefore, preventive measures and timely treatment are important.
To learn about prevention and removal techniques, read the following:
What Causes Efflorescence – The Mechanism Behind Its Formation
Efflorescence is the deposition of crystalline salts either on the surface or within the pores of masonry materials. If efflorescence appears, there must be moisture present inside the structure.
The basic mechanism involves three necessary conditions:
- Presence of soluble salts
- Presence of water
- A path for water migration (capillary action)
Water dissolves soluble salts and transports them to the surface through capillary action. When the water evaporates, the salts remain as visible deposits.
Moist conditions, rainwater infiltration, dew, internal leakage, or use of saline water during construction can contribute to efflorescence formation.
From a chemical perspective, hydration of Portland cement produces calcium hydroxide (Ca(OH)2). This compound can migrate to the surface with water and react with carbon dioxide (CO2) in the atmosphere, forming calcium carbonate (CaCO3). This reaction contributes to efflorescence in cement-based materials.
In addition, soluble hydroxides and sulfates of sodium and potassium—originating from cement, aggregates, water, or admixtures—can accelerate efflorescence formation.
Types of Efflorescence
Efflorescence is generally classified into two types:
Primary Efflorescence
This type occurs during the early curing phase of concrete or masonry. When excess water moves to the surface carrying lime or soluble salts, primary efflorescence forms.
Secondary Efflorescence
Secondary efflorescence develops after the concrete has hardened. It occurs when external water containing soluble salts infiltrates the structure over time. After evaporation, white or grey deposits appear on the surface.