The Bond Behavior of Corroded Reinforcing Bars in Concrete, 1

This paper presents the effects of corrosion on bond behavior of reinforcing bars. Pull-out and push-out tests were performed for specimens of 15cm cube with a deformed bar D19 at the center where the bar was electrolytically corroded before the tests. The bond characteristics of specimens with corroded and non-corroded bars are investigated from the test results. The following results are obtained from the test. 1. Initial surface cracks started when the cumulative current of 5 to 8 amp. hrs. was observed and the width ranged from 0 to 0.20mm. 2. Failure pattern of all specimens was splitting failure. 3. Total slip up to failure at free end with an electrolytically corroded bar was 1/5 to 1/10 times the one with a non-corroded bars. Existence of surface cracks due to corrosion of the bar has no effect on the slip. 4. As for the specimens with cumulative current of less than 5 amp. hrs. when no cracks was observed, the bond strength of electrolytically corroded bars (σ_) was equal to or grater than one of non-corroded (σ_). 5. The value of σ_ / σ_ dropped to 0.50 for the specimens with relatively small cracks showing cumulative current less than 8 amp. hrs. and scattered in the range of 0.25 to 0.50 for the ones having maximum crack width of 0.20 to 0.60mm where cumulative current of 9 to 17 amp. hrs. was observed. It seems that the variance of these values was caused by the existence of defferent internal cracks. 6. For the specimens reinforced with a spiral bar around the center main bar where cracks obsereved, there was no reduction in bond strength and ductile capacity in bond. It is concluded that the reinforcement with a spiral bar around the center contributed beneficially on splitting bond failure