File:2ndary efflorescence 01.jpg

English: Secondary efflorescence, washing out components of cement stone, thus weakening the concrete. In this case, remedial work has already been done once, as can be seen in the concrete patches. But the cause for this "concrete osteoporosis" was not fixed, which means that the damage continues. It is possible to prevent this problem through a better concrete mix design as well as through the use of an impervious, covalent barrier on top. This is the bottom of a slab as seen from the second level of parking in a hotel in Ottawa, Ontario, Canada. Cars with road salt drive in on the upper level, the salty water comes off the cars and then wash out minerals from the cement stone, which winds up as ugly-looking tumors below. The tumor analogy is apt, because, if unchecked, this process will continue to weaken the concrete. In primary efflorescence, one only loses matter that odes not get bound in the cement stone. In secondary efflorescence, one loses matter that originally made the concrete strong.