1994 Fiscal Year Final Research Report Summary
Deterioration Mechanism of Concrete Structures due to Acid Rain
| Project/Area Number |
05452229
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
土木材料・力学一般
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| Research Institution | CHIBA INSTITUTE OF TECHNOLOGY |
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Principal Investigator |
KOBAYASHI Kazusuke CHIBA INSTITUTE OF TECHNOLOGY,CIVIL ENG.DEPT., PROFESSOR, 工学部, 教授 (10013096)
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| Co-Investigator(Kenkyū-buntansha) |
MORI Yahiro CHIBA IONSTITUTE OF TECHNOLOGY CHIBA INSTITUTE OF TECHNOLOGY,CIVIL ENG.DEPT,LECT, 工学部, 講師 (20083884)
UNO Yuuichi SHO BOND CORPORATION,TECHNICAL RESEARCH LABORATORY,CHIEF RESEARCHER, 化学研究所, 課長(主任研究員)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Acid Rain / Concrete / C-S-H / Pore Solution / Carbonation |
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| Research Abstract |
The majour results of this study are the two of 1) that concrete structures throughout Japan are being subjected to the effects of acid rain, and 2) that the deterioration mechanism of cconcrete structures due to acid rain has been brought to light. For confirmation of concrete having been subjected to the effects of acid rain, it is necessary to detect that nitrogen oxides which by nature should not be existing in concrete are contained in outdoor concrete structures. Since nitrogen oxides readily gasify and become diffused, it is difficult to apply analysis generally used on cement concrete. Equipment for analyzing gases contained in metals was used in this study to ascertain that considerrable amount of nitrogen oxides were contained in concrete structures at various locations in Japan, along with which it was shown possible for nitrogen oxides in concrete to be quantified by ion-exchange chromato-tography used in analyzing pore solution in concrete. Concrete is fundamentally a high
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ly alkaline material, and it may be considered that if a sound concrete structure there is little possibility for it to be rapidly deteriorated by acid rain. However, in a structure with concrete having cracks or which is porous and inferior in quality, rain water will easily penetrate into the interior of the concrete so that there will be risk of alkalinity of the concrete rapidly being lowered. Based on these viewpoints, the relationship between decline of pH of pore solution contained in concrete and decomposition of C-S-H comprising hardened cement objects was investigated by model experiments in this study.Furthermore, analyzes were performed on samples collected from conerete structures which had been affected by acid rain, and it was ascertained that C-S-H had been prominently decomposed. The deterioration mechanism of lowering of pH of pore solution due to acid rain and the resulting decomposition of C-S-H causing deterioration of a concrete structures to be accelerated was verified through the above. Less
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