Experimental study on cracking behavior of concrete containing hole defects

Abstract

Cavity often exists in the mass concrete when insufficient vibration occurs. These defects play an important role in the failure mechanism of concrete. Cracking behavior of surface flaws in concrete is widely investigated, while research on failure mechanism of internal flaws is limited because it is difficult to cut internal flaws in specimens and cannot capture the cracking processes of internal flaws through direct observations. In this study, a novel method for preparing concrete samples with embedded flaws is first proposed by volatilization of camphor. AE and CT techniques are adopted to investigate the internal damage failure behavior of hollowed concrete. Experimental results demonstrate that internal hole defects result in a reduction of strength and deformation properties of concrete materials. The peak strength, crack initiation stress, and deformation properties of hollowed concrete specimen decrease with the cavity diameters. Since hole defects induce high stress concentration which exacerbates crack initiation, AE events of specimen with an internal cavity occurred much earlier than the case of intact specimen. The ultimate failure modes of concretes are dominated by tension failure. For intact specimens, tension cracks mainly happen near to the boundaries of specimens. While for hollowed specimens, tension cracks initiated at the cavity perimeter, which then propagated to the boundaries of specimens.