Monitoring of self-healing in concrete with micro-capsules using a combination of air-coupled surface wave and computer-vision techniques

This study mainly aims to investigate the applicability of the combination of air-coupled surface-wave and computer-vision techniques to the evaluation of self-healing in in situ concrete members. Small-scale beam specimens were made from ordinary concrete and concretes with solid- and liquid-type capsules; the capsules were employed as self-healing agents. To monitor the crack healing progress, surface-wave tests using an air-coupled transducer and contact receivers were conducted on each specimen in uncracked, cracked, and healed conditions after 7, 14, 28, and 63 days of water immersion. Additionally, a computer-vision technique involving image binarization and registration was applied to measure high-resolution crack information. The specimens containing the micro-capsules showed superior healing performance compared to the ordinary concrete specimens. After 63 days of self-healing, the spectral energy transmission ratio increased up to about 80% of the uncracked, while the crack area decreased up to about 94% of the fully cracked. The healing rate was estimated using the change in spectral energy transmission ratio strongly correlated with that estimated using the change in crack area.

Automated summary

This study evaluates the self-healing of in situ concrete members using a combination of air-coupled surface-wave and computer-vision techniques. Results show that specimens containing micro-capsules have superior healing performance compared to ordinary concrete specimens, with the healing rate strongly correlated with the change in crack area.