Anti bacterial admixtures are used against organisms like insects, fungi or bacteria that affects the property of concrete. Bacterial affect is not minor effect to concrete, but they affects very adversely. Organisms release corrosive chemicals through their metabolic action on the concrete surface. These chemicals make a different environment that surrounds the concrete which promotes corrosion of steel.
Anti Bacterial Effect
Usually there are two main corrosive agents in bacterial attack. One is the organic acids and the second one is the mineral acid. These acids react with the hydrated cement paste. In the beginning, alkaline pore water in the mix and neutralizes the release acid. After passing few hours, when quantity of release acid become more than the alkaline pore water or when all water is being used for the neutralization of acid then, bacterial attack goes even more deeper to the concrete.
This happens because of the rough surface of the concrete which provides a shelter to the bacteria for growth of bacterial agent. Bacterial agent can be removed by clearing the concrete surface but, as there are still few germs left behind. So, this method is very ineffective. A complete remedy for the bacterial agent is to add some special admixtures in the fresh concrete mix. These admixtures should be act as a toxic agent against the attacking organisms.
Copper sulphate and pentachlorophenol stops the growth of lichen or algae on the surface of hardened concrete. Insecticidal controls the growth of bacteria.