Ultrasonic characterization of small-sized concrete laboratory specimens

Ramaniraka, Manda; Aix-Marseille University; France

Ramaniraka, M.; Aix Marseille Université; France
Rakotonarivo, S.; Aix Marseille Université; France
Garnier, V.; Aix Marseille Université; France
Chaix, J.-F.; Aix Marseille Université; France

ID: ECNDT-0114-2018
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Session: Civil Infrastructure-Concrete 1
Room: J1
Date: 2018-06-13
Time: 09:00 - 09:20

A good management of civil engineering infrastructures depends on a reliable diagnosis about their state of health. Many of them are made of concrete. It is a very heterogeneous material, which consists of aggregates of different sizes within a cement paste. Ultrasonic waves have shown over the recent years a promising potential for Non Destructive Testing of concrete. They are strongly scattered by these heterogeneities in all directions, allowing to probe a large area of the medium. Taking advantage of this phenomenon, this work aims at analyzing scattered waves and especially backscattered ones. Very often, only one side of the infrastructures are indeed accessible for inspection (nuclear containments for example), so that only backscattered waves could be available.

After several mean free paths of propagation, the coherent part of the ultrasonic wave vanishes leaving an incoherent part, called coda. Thus, methods based on the analysis of the coherent part may be inefficient. On the other hand, the coda, closely linked to the microstructure of the medium, carries information about the medium. We compute and analyze the spatial and temporal evolution of the averaged intensity of signals. Fitting this evolution with a theoretical propagation’s model based on the diffusion assumption allows to assess diffusion parameters as diffusivity and dissipation.

Numerical simulations were carried out for different structures configurations to test impact of density of aggregates, medium elasticity or boundary conditions on diffusion parameters evaluation. Different methods are tested to characterize the medium through diffusion theory and information from backscattered signals and from forward scattered signals are compared.