Non-destructive testing for steel columns corroded on concrete boundary

Recently, research has considered the problem of steel columns and signposts corroding at the boundary with concrete in Japan. It is difficult to detect such corrosions visually. Furthermore, steel-concrete composite joints are usedin many bridges and buildings in Japan. In composite joints, the steel members are embeddedin concrete slabs or concrete footings and corroded. lt is therefore necessary to develop a non-destructive inspection method for identifying such damage. Few studies have shown how to locate corrosion on steel embeddedin concrete. In this study, specimens imitating standard steel columns and signposts were damaged so as to obtain basic data on non-destructive inspection of steel-concrete composite joints. In electric corrosiontests of1-shaped steel columns and pipes embeddedin concrete, we examined the relationship between corrosion ratio (amount of steel corrosion) and vibration characteristic (resonance frequency, damping coefficient and ultrasonic velocity). In the steel corrosion tests, the corrosion ratio was about 40%. Our results found that the velocity of supersonic waves traveling through footings containing composite joints decreased as the corrosion ratio increased. Resonance frequency of concrete footing also decreased, but only slightly.