Assessment of crack repairing in concrete using air-coupled surface-wave technique: Experimental and numerical investigations

Abstract

This study aimed to investigate the effectiveness of air-coupled surface-wave techniques for the evaluation of crack-repairing (filling) progress in concrete. Experimental tests were performed on four lab-scale slab-shaped concrete specimens for their uncracked, cracked, and repaired conditions. A structural crack with 0.6- to 0.7-mm wide at the mouth was generated at the midspan of each specimen. The specimen was repaired using an epoxy injection method, and the hardening progress of the injected epoxy was monitored by surface wave measurements for the following 24 hours. Finite element analyses were performed as well to simulate the crack-repairing process by changing the elastic modulus of the repaired zone and quantify the surface wave transmission across the repaired crack. The experimental results revealed that the surface-wave transmission ratio in the fully repaired specimen was recovered up to 90.5 % of the uncracked condition. The numerical analysis showed that, when the elastic modulus of the repaired crack zone reached approximately one-tenth of that of concrete assuming fully-hardened epoxy, the surface-wave transmission ratio was recovered up to approximately 90 % of the uncracked condition. These results imply that air-coupled surface-wave techniques are deemed effective for evaluating crack-repairing performance in concrete.