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
There are two types of efflorescence; primary and
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.