| Summary: | 碩士 === 中華大學 === 建築與都市計畫學系碩士班 === 87 === ABSTRACT
The contamination of chloride ion in reinforced concrete with poor concrete quality, can cause the reinforced steel of concrete corrode easily. The corrosion of reinforced steel is a major cause of structure failure of reinforced concrete. This study elaborates that the reinforced concrete samples with different concrete strengths cover depths, different chloride ion contents, bonded with steel and FRP plates and were utilized to measure the change of corrosion rate of reinforced steel due to the plate bonding method by using AC Impedance method. It is aimed to study effect the plate bonding on the corrosion rate of reinforced steel under different cover depths, chloride ion contents and plate bonding materials.
The results of this study are as follows:
1. In the range of chloride contents studied, the corrosion rate of reinforced steel is reduced by 0.03μA/㎝2～0.27μA/㎝2 indicating that the supply of water and oxygen decrease after the samples are plate bonded.
2. At chloride ion content below 1.82 kg/m3, the corrosion rate is not high and between 0.05 μA/㎝2 and0.5μA/㎝2 before samples were plate bond. Therefore, the effect of the plate bonding on the corrosion rate of reinforcement is significant.
3. When chloride ion content reach 5.46 kg/m3, the reinforced steel corroded very seriously. The corrosion rate are between 1.71μA/㎝2 and 2.84μA/㎝2. Since the concrete contaminated with chloride ion has tendency to absorb humidity and to reduce concrete's electrical resistance. Thus the corrosion rate of reinforced steel reduce slightly after the bonding of steel and FRP plates.
4. Water cement ratio affects the porosity of concrete, consequently affects the vaporization of water in concrete and the ability to absorb humidity in concrete. Therefore, it has a profound effect on the corrosion of reinforced concrete when concrete is bonded with steel and FRP plates.
5. When the concrete bonded with steel and FRP plates, the electrical resistance of concrete increase for both cases. This indicates that above two materials have the same effects on reducing the penetration of water and oxygen into concrete.
6. The depth of cover affects the water content at the concrete surrounding the reinforced steel. In this study, the relative humidity of test environment is comparative low. Therefore, when the depth of cover is thin, the water content at the concrete surrounding the reinforced steel vaporizes easily. Consequently, the water content is low after it was bonded with plates and the electrical resistance of concrete increases, and resulting in the decrease of the corrosion rate of the reinforced steel. On the contrary, when depth of cover is larger, the residual water content is high, and the corrosion rate will not decrease easily. But in actual environment, humidity can be higher than that of test environment, therefore, after plate bonding the electrical resistance of concrete will not increase easily, the corrosion rate of the reinforced steel will not decrease easily when the depth of cover is small.
7. The effect of the plate bonding on the reduction of the corrosion rate is around 0.2 μA/㎝2. The feasibility of plate bonding on corrosion protection of the reinforcement in concrete is determined by the corrosion rate before the plate bonding. The higher corrosion rate before the plate bonding the lower effect of the plate bonding. For example, if corrosion rate is above 1μA/㎝2, the effect of the plate bonding is below 20%.Therefore ,to assess the feasibility of using the plate bonding method to protect the reinforcement ,one must inspect the corrosion rate of the reinforced steel ,and utilize it as the reference base for evaluation of the effectiveness of using the plate bonding methods.
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