Application de la tomographie sonique au diagnostic du béton

Abstract

Recognition of the many problems in concrete structures requires the reconstruction of their internal image. For this reason, some years ago, a new nondestructive method, sonic tomography, has been developed for scanning concrete structures. This method is most often based on transient stress wave propagation for verifying a concrete body, as well as measuring the wave velocity. The relative variation in wave propagation velocity in the material provides information about changes in the structure, and therefore the state of degradation. Capacity and limitation of this method for reconstructing the internal image of the concrete structures are addressed in this thesis. This study discusses some experiments in which sonic tomography were performed on various concrete models in laboratory and the structures in service in-situ. In this case, two important aims are the main focus: (1) Degraded area is usually marked by fracture and delaminations or poorly performed sections within the structure. Unfortunately, most of the degradation in concrete structures remain undetectable to the naked eye. Sonic tomography is a strong technique to show the damaged areas in body concrete. In addition, this technique is able to evaluate internal reparation (e.g. control of grout-injection zones). (2) This is limited by the measurement and reconstruction of image conditions and their parameters (frequency, pixels size, rays type, measurement step,...). For illustrating the real image it is necessary to know precisely these conditions and the quality of their influence on the tomographic image.