コンクリート中の鉄筋の発錆実験 その2 －9ケ月および１ケ年時点－
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概要
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This is the second report of experiments on corrosion behavior of steel bars embedded in concrete. Previous report has included the results of tests done at three and six months after embeded. This reports the results of experiments done at nine and twelve months. The experiments was planned by the method of so called "experimental design." The experiments are composed of two series of test programs. The first series of tests are consists of 32 tests in accordance with L₃₂ (2³¹) table and the second one is performed by the program based on the L₉ (3⁴) table. The main factors of the first are salt contents in concrete, environmental conditions of specimens, quantities of inhibitor, water cement ratios, and concrete cover depths over steel bars. Four main factors included in the second program are kinds of inhibitors, quantities of inhibitors, salt contents, and heating conditions of the specimens. The corroded areas of steel bars embedded in concrete were measured at the times when 3, 6, 9, and 12 months passed after specimens were made. In these experiments, the salt contained in specimens amount to very high quantities, which correspond the high salt contents of the existing reinforced concrete structures in Okinawa Prefecture, and are also distinctive feature of these experiments. The following facts are found in this study: 1. The corroded areas of the steel bars embedded are steadily increased as the progress of time, in which sometimes rapid increasing are observed due to cracking along steel bars. 2. The initiation times of cracking in these experiments are mainly dependent on concrete cover depth over steel bars and water cement ratio of concrete. 3. An overwhelming strong influence of salt content on the corrosion of steel bars sometimes disturbs the effects of other main factors of these experiments. 4. A very beneficial effect of 40% water cement ratio and a deterimental effect of concrete cover depth of 1cm are observed. 5. Optimum dosage quantities of inhibitors seems to be existed and are dependent on the salt contents of the concretes. Fixed standard quantities of inhibitors' dosage directed by makers must be withdrawn. The enough quantities of inhibitors must be added to concrete which are dependent on the salt contents of concretes. 6. In Okinawa Prefecture, the makers' standard quantities of dosage of inhibitors are to be not enough to inhibite the corrosion of steel bars, because of the high salt contents of sea sands in this region. 7. It had better not use inhibitors in the reinforced concrete structures which stand in the sea water or near beaches, because high salt condition in the concrete will be brought in near future. In the case of high salt concentrations in concrete, the beneficial effects of inhibiters disappear or become rather harmful. 8. When high salt condition exists in concrete, it can not be prevented steel bars from serious rusting by minimizing the water cement ratio, increasing the thickness of concrete cover over steel bars, and increasing the dosage of the amount of inhibitors in concrete.
- 琉球大学理工学部の論文
- 1978-09-01
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