コンクリート中の鉄筋の発錆実験　その1－3ヶ月時と6ヶ月時（その1）－

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It was clarified by the authers' site investigations that many of the reinforced concrete structures in Okinawa Prefecture are seriously damaged and deteriorated due to corrosion of steel bars embedded in concrete. The authers concluded that the situation was so serious that some protective measures must be taken as soon as possible. Many factors are responsible for the above damages, e.g., faults at construction stage, low qualities of concrete used, carbonation of concrete, the use of sea sand, the use of brine water, directly attacks of sea water, and etc. To improve the above situation, this experimental study was planned. About 450 pieces of concrete specimens, 12×20×3O cm rectangular cylinders are manufactured, and they contained three bars each. The experiments are planned and performed by the method of so called "experimental design". The experiments consist of two series of tests, one consists of 32 experiments in accordanced with, L₃₂ (2³¹) table, and the other is composed of 9 experiments in accordance with L₉ (3⁴) table. The main factors of the former experiment are salt content of concrete, surrounding condition of specimens, water cement ratio, the quantity of inhibitor, and thickness of concrete cover over steel bars. Four items, the kind of inhibitor, the quantity of inhibitor, salt content, and heating of specimen, constitute the main factors of the latter experiment. The effects of these experiments are surface area of corroded region of steel bars. The area corroded are measured at three and six months after manufactured. The following items clarified in this study must be mentioned: 1) The salt content is the overwhelming factor which effects the corrosion of steel bars. 2) In high salt content concrete, increasing the thickness of concrete cover over steel bars, lowering the water cement ratio, and increasing the inhibitor quantity used are not useful for decreasing the area of corroded region of steel bars embedded in concrete. On the other hand, in low salt content concrete, the above measures are useful for prohibiting the corrosion or decreasing the corrosion area. 3) In using corrosion inhibitors, it must be remembered that the enough quantity of inhibitors has to be used, otherwise it effects adversely. 4) The measures, increasing the thickness of concrete cover, lowering the water cement ratio, and using corrosion inhibitors, can not inhibite the initiation of the steel bar corrosion when some quantity of salt exists in concrete. 5) In discussing the inhibitor's effects. it must be judged by the longterm investigations. In spite of no corrosion at three month's measurment, steel bar rusting are developed at 6 month's test. 6) The heating the specimens at 50℃ has accelerating effect in rusting steel bars embedded. 7) Judging from the high salt content of the sea sand used commonly in Okinawa Prefecture, the quantity of inhibitor to be used reccomended by makers are not enough for prohibiting the corrosion of steel bars embedded in concrete.
琉球大学理工学部の論文
1978-03-01

コンクリート中の鉄筋の発錆実験　その1－3ヶ月時と6ヶ月時（その1）－

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コンクリート中の鉄筋の発錆実験 その1－3ヶ月時と6ヶ月時（その1）－

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コンクリート中の鉄筋の発錆実験　その1－3ヶ月時と6ヶ月時（その1）－