Healing and simultaneous ultrasonic monitoring of cracks in concrete

Premature cracking is a prime cause for deterioration of concrete structures. Techniques, especially wave-based technologies, have been developed for monitoring deteriorations of such structures. Recently, techniques for healing of the deteriorations are emerging necessitating expansion of monitoring techniques to healing as well. This paper reports experimental results for healing of cracks of different widths in concrete and illustrates the ability of the ultrasonic techniques to monitor the progression of healing. A numerical technique based on two-dimensional finite difference time domain (FDTD) has been used to determine the potential of the ultrasonic stress waves in monitoring healing. Based on the theoretical results, an experimental study has been conducted on reinforced concrete samples by creating a fine tensile crack of width similar to 0.1 mm and a relatively wide corrosion crack of similar to 2 mm width. They were monitored ultrasonically after cement grout was injected in the cracks. It is found that the ultrasonic technique is able to discern the progressive healing process. Signal attenuation was found to be most suitable for monitoring healing.