Continuous condition monitoring of reinforced concrete using an active diagnosis method

Abstract

In the reinforced concrete structures, the reinforcement such as a steel bar plays an important role in load bearing. The condition monitoring of the steel bars in the concrete is very relevant. An active transmit/receive (pitch–catch) method was employed to assess debond state between the steel bars and concrete. When a wave is excited at one end of a steel bar and received at the other end, it can bring the damage information about the interface of the steel bar and concrete. A set of reinforced concrete beams under flexural loading were carried out, and the pitch–catch monitoring was performed in static, quasi-static, and continuous loading state, respectively. The results show that the amplitude of the receiving wave presents an obvious regularity in each condition. Both the static and quasi-static tests provide a steady state and reflect post-debond states. While the continuous monitoring provides a more comprehensive and more sensitive result, which can reflect the continuous change in debond state. However, the receiving signals in continuous monitoring are faced with the confusion of the acoustic emission signals which come from various damages. By reasonable signal processing, the pitch–catch signals are isolated from a large number of acoustic emission signals. Two distinguishing features of the amplitude curve reflect two critical damages which can provide early warning of civil engineering structures.