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Title |
The Damage Investigation of Sewer Pipe Surge Tank Concrete Experienced Sulfur Biodeterioration
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Authors |
지석원(Suk-Won Ji) ; 염광수(Kwangsoo Youm) ; 김정중(Jung J. Kim) ; 문지호(Jiho Moon) |
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DOI |
https://doi.org/10.4334/JKCI.2017.29.6.641 |
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Keywords |
생물학적 열화 ; 황화수소 ; 황산침식 ; 산성침식 ; 중합화 biodeterioration ; hydrogen sulfide ; sulfate attack ; acid corrosion ; polymerization |
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Abstract |
The sulfur-oxidizing bacteria oxidizes H2S gas in sewage as H2SO4 and the concrete can be severly damaged. This is called the biodeterioration of the concrete. In this study, the visual inspection for the surge tank, which service life came into over 14 years, was performed. Also, the change of microstructures in the concrete of the surge tank was investigated. The yellowish brown discoloration on both the internal and external concrete surface of the tank was observed. The discolored internal concrete surface was mushy and spalled due to the disintegration of microstructures in hydrated cements, while the discolored external concrete surface was not spalled since the discoloration was due to accumulation of sulfide resulting from leaking H2S gas. The biodeterioration rate was estimated as 1.43 mm∼3.93 mm/yr and there was no significant decrease in compressive strength of concrete. Microstructures in hydrated cement were analyzed by TGA, XRD, 29Si MAS NMR, and Ion anion chromatography. It was found that portlandite was depleted to react with sulfuric acid and the production of gypsum was confirmed on internal concrete surface. Furthermore, silicate polymerization due to the calcium leaching from C-S-H was observed by NMR experiments.
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