Efflorescence in concrete is a whitish coloured powdered deposition of salts on the concrete surface that is formed due to evaporation of water from the concrete. It is caused when water soluble salts are present in the concrete material, which comes on to the surface while evaporation of water from the concrete.
Causes for Formation of Efflorescence in Concrete
The formation of efflorescence in concrete is factored by many external factors.
1) Presence of salts in one of the materials of concrete. Commonly salts are found in the fine aggregate or sand taken from the river beds.
2) If the concrete is not cured properly, the hydration process is incomplete on which the un-hydrated products near the surface form the efflorescence on the surface of concrete.
3) Slow rate of evaporation of water allowing time for salts to permeate to the surface (this is why efflorescence tends to be more of a problem during the winter months; in summer, high temperatures may cause evaporation and hence depositing of salts within the concrete rather than on the surface)
4) If the water content in the concrete mix is more, it makes the concrete porous. Thus allowing the path for water and salts to come to the surface and for efflorescence.
5) In wet conditions such as rainy season, the surplus water acts as a medium for the salts to transport to the surface of concrete and form crystalline white powder.
6) Variability of concrete (compaction or curing) can result in localised problems where water can permeate more easily through the concrete.
Type of Salts in Efflorescence:-
a) Calcium Sulphate- A common efflorescence salt source in brick
b) Sodium Sulphate- Often seen in cement-brick reactions
c) Potassium Sulphate- Noticeable in many cement-brick reactions
d) Calcium Carbonate- May be discovered in mortar or concrete backing
e) Sodium Carbonate- Frequently seen in mortar
f) Potassium Carbonate- Like sodium carbonate, commonly found in mortar
g) Vanadyl Sulphate- Usually found in brick
h) Manganese Oxide- Often present in brick.
2) If the concrete is not cured properly, the hydration process is incomplete on which the un-hydrated products near the surface form the efflorescence on the surface of concrete.
3) Slow rate of evaporation of water allowing time for salts to permeate to the surface (this is why efflorescence tends to be more of a problem during the winter months; in summer, high temperatures may cause evaporation and hence depositing of salts within the concrete rather than on the surface)
4) If the water content in the concrete mix is more, it makes the concrete porous. Thus allowing the path for water and salts to come to the surface and for efflorescence.
5) In wet conditions such as rainy season, the surplus water acts as a medium for the salts to transport to the surface of concrete and form crystalline white powder.
6) Variability of concrete (compaction or curing) can result in localised problems where water can permeate more easily through the concrete.
Type of Salts in Efflorescence:-
a) Calcium Sulphate- A common efflorescence salt source in brick
b) Sodium Sulphate- Often seen in cement-brick reactions
c) Potassium Sulphate- Noticeable in many cement-brick reactions
d) Calcium Carbonate- May be discovered in mortar or concrete backing
e) Sodium Carbonate- Frequently seen in mortar
f) Potassium Carbonate- Like sodium carbonate, commonly found in mortar
g) Vanadyl Sulphate- Usually found in brick
h) Manganese Oxide- Often present in brick.
