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

Abstract

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.

Fundamental Properties and Self-Healing Performance of Repair Mortar with Solid Capsules Made Using Inorganic Reactive Powder

“…Figure 15 shows the scanning electron microscopy (SEM) images of the healing products. It was observed that the healing products consisted of hexagonal crystals of calcium hydroxide and needle-like crystals of C-S-H [ 34 , 35 ].…”

Non-destructive evaluation of the effects of exposure environment in mortars using non-linear ultrasonic measurements

“…), or material development properties. The most important wave-based methods for evaluating damages in structures made with concrete are: acoustic emission (AE) (Ospitia et al, 2023), impact echo (IE) (Fülöp et al, 2022), ultrasonic pulse velocity (UPV) (Revilla-Cuesta et al, 2022), surface-wave techniques (Lefever et al, 2022(Lefever et al, , 2023Ahn et al, 2018Ahn et al, , 2022aIn et al, 2015) and diffuse-wave techniques (Quiviger et al, 2012;Payan et al, 2013;In et al, 2017;Zhang et al, 2018;Ahn et al, 2022b) for monitoring and evaluation of healing, cracks or discontinuities in concrete.…”

Enhanced generation and reception of ultrasonic Rayleigh waves through in-phase superposition of waves: theory and experiment

“…Comb transducers [12,13], electromagnetic acoustic transducers (EMATs) [14], interdigital transducers (IDTs) [15], and angle beam wedge transducers [16] are widely used in ultrasonic detection using Rayleigh waves. In addition, Rayleigh waves can also be generated when a piezoelectric (PZT) element rests on the edge of the sample [17], a point or line laser beam acts on the surface [18], an air-coupled transducer incidents wave obliquely to the solid surface [19], and an X-or Y-cut plate is located on the surface of the specimen [4]. In this work, the above transducers are grouped into two categories according to the type of excitation source.…”