Bacterial Corrosion of Concrete

When the powder of corroded concrete is mixed with a culture medium for the sulfur-oxidizing bacteria and the mixture aerobically shaken at 28°C, the pH of the medium decreases within days and the pH usually becomes less than 2 after 10 days of shaking. The precipitate collected by centrifugation of the culture medium after 10 days of shaking contains bacteria, as shown in Fig. 4.9. 

In the corroded concrete, there also reside acidophilic iron-oxidizing bacteria (see below) besides the usual sulfur-oxidizing bacteria. The acidophilic iron-oxidizing bacteria show optimal growth pH at 2.0, and oxidize not only ferrous iron but also sulfur compounds. Therefore, they can participate in the corrosion of concrete. We have to consider the action of both the usual sulfur-oxidizing bacteria and the acidophilic iron-oxidizing bacteria when we exploit the compounds which inhibit the bacterial corrosion of concrete. 

Are there any methods to inhibit the growth of the bacteria participating in the corrosion of concrete A few compounds have been exploited which inhibit the growth of the sulfur-oxidizing and acidophilic iron-oxidizing bacteria. A reagent 

The author and his colleagues have found that calcium formate completely inhibits the growth of the sulfur-oxidizing bacteria and acidophilic iron-oxidizing bacteria at 50 mM (6500 ppm) or more in laboratory experiments (Yamanaka et al., 2002a). Calcium formate is hardly harmful and as it will finally become calcium carbonate, it is expected that the compound will barely pollute the environment. 

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