2HX + Ca(OH)2
-Æ CaX2
+ 2H2
O
(X is the –ve ion of the acid)
Depending on the porosity of the cement concentration of the
acid, the solubility of acid calcium salts (CaX2
) paste, the
decomposition of the concrete depends. Insoluble calcium
salts may precipitate in the voids and can slow down the attack.
Acids such as H2
SO4
, nitric acid, Hydrochloric acid, acetic
acid are very aggressive as their calcium salts are readily soluble
and removed from the attack. Sulphuric acid is very damaging
to concrete as it combines an acid attack and sulphate attack.
HCl has a mild attack and Na2
CO3
is negligible.