“Concrete sewer structures and pipes are corroded by sulphuric acid which destroys the cement binder and ultimately results in corrosion of the reinforcing steel. Sulphuric acid is produced in sewers by a complex chain of microbiological and gas/liquid solubility stages which occur as the sewage travels through the sewerage system. These bacteria can create levels of sulphuric acid concentrations as high as 7%. This acid diffuses into the concrete structure, destroys the cement gel binder, and forming soft and soluble gypsum (calcium sulphate hydrate)”.

“KALMATRON® KF-A admixture to concrete mixes is a conceptually new product patented in the USA . This is an inorganic oxidizer of micro/macro metal elements contained in cementitious materials providing electro-chemical decay of cement grain by electrolysis between inversely charged particles of electrolyte and cement grain.

Decay-hydration reactions result in maximum hydration/decay of cement grains and volume of cementitious paste as a continuous solid phase in which the aggregates are embedded.

Extension of the gel surface classifies KALMATRON® KF-A with admixtures known as Type C – accelerating admixtures, and Type F – water-reducing, high range admixtures”.

Any ingredient of the concrete batch with certain sorption ability is vulnerable to any liquid/gas corrosion. The photograph at right shows corroded coarse aggregate when cementitious paste protected by KF-A was perfectly intact. Therefore, completed cement grain hydration by KF-A admixture do not leave agential volume for any acidic reaction.

Left picture- The attack of concrete cementitious part takes place mainly above the normal sewerage flow level. Sewage is rich in sulphur-containing materials, both organic (protein, etc) and inorganic (sulphates, etc).
Right picture- Above: concrete with KF-A applied on the floor of a zinc plant, where the cementitious part of the concrete was intact after one year but the dolomite-like aggregate was eaten up by the sulfuric acid, and that floor looked like a honeycombed surface. It was recommended to use a denser brand of aggregate.