Study of concrete alteration in sewer systems by biogenic sulfuric acid
ABSTRACT: Concrete used in sewer systems is exposed to a very aggressive environment. Indeed, the effluents contain organic and inorganic sulfur compounds allowing to be consumed by sulfate-reducing bacteria to form gaseous hydrogen sulfide which condenses on the emerged walls. Then, this last compound is oxidized by sulfur-oxidizing bacteria in sulfuric acid. The study of the bacterial growth medium and the characterization of degraded c oncrete by the action of the biogenic H2SO4 are carried out by ESEM observations associated with EDS microanalyses. The decrease of concrete properties according to the duration of biodegradation is highlighted by the structural modifications of concrete. These results are completed by liquid phase analysis allowing to perform a chemical assessments of the dissolved species in the solution. Complementary tests such as degraded thickness of the concrete specimen and weight-loss measurements improve the comprehension of phenomena which contribute to the mechanisms of degradation of concretes.