1992 Fiscal Year Final Research Report Summary
RESEARCH ON PREVENTING REINFORCING BAR CORROSION IN CONCRETE STRUCTURES CAUSED BY CHLORIDES IN SEA SAND
| Project/Area Number |
02555124
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Building structures/materials
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| Research Institution | THE UNIVERSITY OF TOKYO |
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Principal Investigator |
TOMOSAWA Fuminori UNIV. OF TOKYO, FACULTY OF ENGINEERING, PROFESSOR, 工学部, 教授 (50211404)
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| Co-Investigator(Kenkyū-buntansha) |
YAMASAKI Satoshi NISSAN CHEMICAL INDUSTRIES, CENTRAL RESEARCH INSTITUTE, CHEMIST, 機能材料研究部, 研究員
HORI Takahiro NISSAN CHEMICAL INDUSTRIES, CENTRAL RESEARCH INSTITUTE, CHIEF CHEMIST, 機能材料研究部, 主任研究員
HARA Kenji ONODA CORPORATION, CONSTRUCTION DIVISION, MANAGER, リフレッシュ事業部, 技術部員
MASUDA Yoshihiro MINISTRY OF CONSTRUCTION, BUILDING RESEARCH INSTITUTE, MANAGER, 第2研究部, 室長
NOGUCHI Takafumi UNIV. OF TOKYO, FACULTY OF ENGINEERING, RESEARCH ASSISTANT, 工学部, 助手 (80208321)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Reinforced Concrete / Repair / Corrosion / Chloride Ion / Corrosion Inhibitor / Low-pressure Injection / Nitrite Ion / Chloride Ion Molar Ratio / Diffusion |
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| Research Abstract |
1. Nitrite Ion/Chloride Ion Molar Ratio above which Corrosion is Prevented
(1) The threshold value of molar ratio increases as the chloride content in concrete increases.
(2) Corrosion of reinforcing bar can be prevented with the molar ratio of 1 or more independent of the chloride content.
2. Effect of Nonuniform Distribution of Nitrite on Corrosion Prevention
(1) Acceleration of corrosion on the anodic sites due to macrocell corrosion is observed when a small zone without nitrite ions exists in the concrete.
(2) No corrosion acceleration due to differential nitrite ion concentrations is observed when nitrite ions are distributed throughout the concrete with the molar ratio of 0.5 or more. Corrosion of reinforcing bar is sufficiently inhibited when nitrite ions are distributed throughout the concrete at the concentration of molar ratio of 1 or more, even if the concentrations are not uniform.
3. Permeation of Nitrite Ions
The low-pressure injection method of corrosion inhibitor enables nitrite ions to permeate concrete fast and in a wide range. However, corrosion inhibitor cannot permeate much in wet condition.
4. Repair Method for Corrosion of Reinforcing Bars
The low-pressure injection method using nitrite corrosion inhibitor can be very effective and practical for corrosion prevention of reinforcing bars in a state of corrosion in which minute cracks are occurring on the surface of concrete.
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