Detecting Onset of Different Types of Flaws in Reinforced Concrete

The experimental results of a novel ultrasonic monitoring method to identify different types of flaws in reinforced concrete are presented. The authors' previous work has demonstrated the ability to use the proposed ultrasonic guided wave leakage (UGWL) to identify the onset of mechanical delamination. This paper presents the results from using the UGWL method to identify chemical delamination (corrosion) and cracking in concrete (other than delamination at the steel-concrete interface) in reinforced concrete. The proposed UGWL method monitors the change in amplitude of ultrasonic waves leaked from a guided wave transmitted through an embedded steel reinforcing bar. The energy of UGWL is influenced by the conditions between the steel reinforcing bar, acting as the waveguide, and the surrounding concrete. This experimental study demonstrated that the UGWL monitoring method is sensitive not only to the onset of delaminations, but also to the development of corrosion activity and cracks.