Efflorescence in Concrete
Efflorescence is the formation of salt deposits, usually white, on or near the surface of concrete causing a change in appearance.
Apart from the discolouration, efflorescence is generally harmless. This is best described as being 'a skin trouble and not a deep-seated disease'.
Primary efflorescence is efflorescence occurring during hardening of the concrete.
Secondary efflorescence is the efflorescence resulting from the weathering of the hardened concrete.
Crypto-florescence is the deposition of salt within the pores of concrete below the exposed surface.
The force of crystallisation growth may cause some fretting.
Light coloured concrete shows the deposit much less than darker coloured concrete.
With time, efflorescence becomes less extensive. Efflorescence is most obvious in the winter, but may be observed throughout the year after a heavy rain and a drop in temperature.
Information Courtesy of CCAA
These pictures show the effects of efflorescence.
Another classic example of efflorescence, this time with colour hardener
This concrete required 3 acid washes, with the concrete being wet down to avoid acid burning.
The acid was applied with enough acid added to the bucket of water to create a sizzle effect when applied to the concrete. A stiff bristled broom was used to vigorously scrub the concrete.
In the last picture, the concrete has not completely dried.