Crack Detection and Evaluation in Grout Structures with Passive/Active Methods

This paper presents piezoelectric-based passive/active methods to reliably detect and quantify defects in mass concrete or grout structures. A dual-mode sensing methodology that makes use of both passive acoustic emission detection and active ultrasonic wave evaluation methods utilizing piezoelectric sensors is investigated. Two types of piezoelectric sensors (PES) transducers are used for acquiring the passive and active signals, respectively. A novel imaging method is developed to map and locate the acoustic emission source caused by the damage growth in the subject structure. Active sensing is further used to evaluate the growth of the damage. A proof-of-concept test using simulated damage, a pencil lead break for acoustic emission, and a drill hole of various diameters for crack growth has been conducted to show the effectiveness of the present passive/active methods. The methods have also been applied to detect and evaluate crack growth caused by stepwise loading. The work presented in this paper lays the foundation for further development of a dual-mode sensing mechanism for in situ crack growth detection and evaluation in massive grout or similar material structures.