Editing Efflorescence (section)

===Secondary efflorescence===
Secondary efflorescence is named such as it does not occur as a result of the forming of the cement stone or its accompanying hydration products. Rather, it is usually due to the external influence of concrete poisons, such as chlorides. A very common example of where secondary efflorescence occurs is steel-reinforced concrete bridges as well as parking garages. Saline solutions are formed due to the presence of road salt in the winter. This saline solution is absorbed into the concrete, where it can begin to dissolve cement stone, which is of primary structural importance. Virtual [[stalactite]]s can be formed in some cases as a result of dissolved cement stone, hanging off cracks in concrete structures. Where this process has taken hold, the structural integrity of a concrete element is at risk. This is a common traffic infrastructure and [[building]] maintenance concern. Secondary efflorescence is akin to [[osteoporosis]] of the concrete.

For controlling secondary efflorescence, admixtures containing aqueous-based [[calcium stearate]] dispersion (CSD) are often added at a later stage of the batching process with the mix water. In a typical batching process, sand is first charged into the mixer, then the oil-based primary anti-efflorescence admixture is added with constant mixing to allow the oil to coat the sand. Then coarse aggregates, colorants, and cement are added, followed by water. If CSD is used, it is then introduced usually at this point during or after the addition of the mix water. CSD is an aqueous dispersion wherein fine solid particles of calcium stearate are suspended in the water uniformly. Commercially available CSD has an average particle size of about 1 to 10 micrometres. The uniform distribution of CSD in the mix may render the resulting [[concrete masonry unit]] water repellent, as CSD particles are well distributed in the pores of the unit to interfere with the capillary movement of water.<ref name=pat648/>

[[Calthemite]] is also a secondary deposit derived from concrete, mortar or lime, which can be mistakenly assumed to be efflorescence. Calthemites are usually deposited as calcite which is the most stable [[Polymorphism (materials science)|polymorph]] of [[calcium carbonate]] (CaCO<sub>3</sub>).<ref>Smith, G.K. (2016). "Calcite straw stalactites growing from concrete structures", Cave and Karst Science 43(1), 4-10. http://bcra.org.uk/pub/candks/index.html?j=127</ref><ref>Smith, G K., (2015). "Calcite Straw Stalactites Growing From Concrete Structures". Proceedings of the 30th 'Australian Speleological Federation' conference, Exmouth, Western Australia, edited by Moulds, T. pp 93 -108</ref>