Efflorescence

Summary

Efflorescence - is a process by which soluble compounds are leached out of concrete, leaving a white deposit on the surface.

Technical Information

Primarily an aesthetical problem in concrete, efflorescence is only an issue when the appearance of the finished concrete floor is important.

Efflorescence happens in all concrete exposed to moisture. It is a process where salts are leached out of the concrete by water and are then deposited on the surface. It doesn’t cause any structural problems.There are two types of efflorescence; primary and secondary:

Primary efflorescence – caused by excess water present in the after setting due to an excessively high water / cement ratio travelling to the surface of the concrete.
Secondary efflorescence – caused by external water travelling from one side of the concrete to the other. Therefore, efflorescence can indicate that the underside of a concrete slab is very damp, especially if it occurs a long time after the slab has initially set. The best way to avoid secondary efflorescence in slabs is to install a waterproof membrane underneath the slab during construction.