Nondestructive evaluation of bar-concrete interface in reinforced concrete structures

Abstract

The feasibility of detecting and quantifying delamination at the interface between steel (or GFRP) bar and concrete using ultrasonic guided waves is investigated in this study. These waves can propagate a long distance along the reinforcing steel (or GFRP) bar or concrete beam as guided waves and are sensitive to the interface bonding condition between the steel (or GFRP) bar and concrete. The traditional ultrasonic methods are good for detecting large voids in concrete but not very efficient for detecting delamination at the interface between concrete and steel (GFRP) bar since they use reflection, transmission and scattering of longitudinal waves by internal defects. In this study, special solid couplers between the steel/GFRP bar (or concrete beam) and ultrasonic transducers have been used to launch cylindrical guided waves (or Lamb waves) in the steel/GFRP bar (or concrete). This investigation shows that the guided wave inspection technique is an efficient and effective tool for health monitoring of concrete structures.