DEGRADATION OF CONCRETE IMMERSED IN SULFURIC ACID FOR A LONG TERM

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  • KAWAI Kenji
    HIROSHIMA UNIVERSITY, Institute of Engineering（1-4-1, Kagamiyama, Higashihiroshima-shi, Hiroshima 739-8527, Japan）
  • OGAWA Yuko
    HIROSHIMA UNIVERSITY, Institute of Engineering（1-4-1, Kagamiyama, Higashihiroshima-shi, Hiroshima 739-8527, Japan）
  • TSUBONE Keisuke
    HIROSHIMA UNIVERSITY, Graduate School of Engineering（1-4-1, Kagamiyama, Higashihiroshima-shi, Hiroshima 739-8527, Japan）
  • YAMAGUCHI Yoshiki
    HIROSHIMA UNIVERSITY, Graduate School of Engineering（1-4-1, Kagamiyama, Higashihiroshima-shi, Hiroshima 739-8527, Japan）

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  • 長期間硫酸浸漬したコンクリート内部の変質

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<p>Many research papers regarding sulfuric acid deterioration of concrete mainly evaluate degradation of concrete near its surface exposed to sulfuric acid, based on the results of immersion tests which are conducted comparatively for a short term using a high concentration of sulfuric acid. However, there are few papers dealing with the degradation of concrete in the vicinity of the Fe layer that is formed around the boundary between acidic and alkaline areas as the result of migration of Fe ions decomposed in concrete deteriorated by sulfuric acid. The present study carried out immersion tests of concrete for the long term of 1,600 days using sulfuric acid at concentrations of pH＝1 and pH＝2, at which concrete in actual structures is deteriorated. After the immersion tests, concrete deeper than the Fe layer was investigated with TG-DTA analysis, XRD/Rietveld analysis and pore structure analysis. As a result, it was found that sulfuric acid penetrates beyond the Fe layer, resulting in formation of gypsum by sulfate ions together with decomposition of hydrates by the acid in concrete deeper than the Fe layer. This result suggests that concrete deeper than the Fe layer could be degraded after long-term exposure to sulfuric acid although the Fe layer can be usually used as an index of the boundary between deteriorated and sound concrete in repair work of concrete deteriorated due to sulfuric acid attack.</p>

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