Deterioration of Concrete Derived From Metabolites of Microorganisms

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Title: Deterioration of Concrete Derived From Metabolites of Microorganisms

Author(s): E. I. Tazawa, T. Morinaga, and K. Kawai

Publication: Special Publication

Volume: 145

Issue:

Appears on pages(s): 1087-1098

Keywords: bacteria; concretes; damage; deterioration; hydrogen; sulfide; metabolites; microorganisms; mortars (material); Materials Research

Date: 5/1/1994

Abstract:
An underground concrete structure in Japan was severely damaged. The structure was located in a soil that contained considerable hydrogen sulfide and the effects of various microorganisms could not be disregarded. In this study, several types of bacteria in the soil around the structure were isolated and cultured, and simulation tests of mortar deterioration were performed to clarify effects of bacteria on concrete deterioration. Hydrogen sulfide-producing bacteria or sulfur-oxidizing bacteria or both were used. Calcium ion was dissolved out of mortar soaked in the culture medium inoculated with hydrogen sulfide-producing bacteria. The value of pH was decreased and the quantity of hydrogen sulfide was increased in the culture medium as growth of the bacteria proceeded. Since this dissolution of calcium ion from mortar was not observed in the control medium, metabolites of these bacteria could be one of the reasons. From the results of TG-DTA, CaCO 3 content in the mortar surface increased and Ca(OH) 2 content decreased. This is because carbon dioxide produced by the bacteria caused carbonation of the mortar. It has already been established that concrete can be severely damaged by anaerobic bacteria, but this study suggests that concrete can also be damaged by metabolites of aerobic bacteria.