Corrosion of Concrete by Autotrophes

Abstract The various types of sulfur bacteria which can be present in concrete sewers are described and conditions which are necessary for their existence are listed. There are three steps in the destruction of concrete sewers by autotrophes: (1) production of hydrogen sulfide by the reduction of sulfates or by the action of proteolytic bacteria, (2) oxidation of the hydrogen sulfide to sulfuric acid by the sulfur bacteria, and (3) decomposition of the calcium silicates of the portland cement by the sulfuric acid. A number of countermeasures which can be taken to prevent these conditions are discussed. They include the designing of sewers for rapid flow, ventilation, and the use of protective coatings. 3.3.4