Quantitative ultrasonic characterisation of concrete damage using a multiple scattering model: Fid-Bau Portal

Quantitative ultrasonic characterisation of concrete damage using a multiple scattering model

Chaix, J.F. / Garnier, V. / Corneloup, G.

The general subject of this study is the non destructive characterisation of concrete damage. Thermal loads on concrete induce the increase of microcracks rate and sizes. The link determination between physical and ultrasonic parameters is possible by effective medium theories which homogenise the physical medium and determine ultrasonic parameters. We studied multiple scattering dynamic models and we adapt the one of Waterman-Truell to the case of damaged concrete. We take into account homogeneous matrix containing air spherical inclusions which simulate damage. Experimentally, we work on cement specimens with aggregates and expanded polystyrene inclusions and measure phase velocity and attenuation. In particular, we observed predicted values of velocity and attenuation in case of damaged medium. For the damage simulated by air spherical inclusions we obtained very good agreement for the velocity on the frequency domain explored. Results in attenuation show good agreement for low frequencies but must be improved for higher ones. In case of thermal damage we obtain similar behaviours on measured velocities and attenuation. Modelling this medium is not possible, for the moment, due to the lack of knowledge about real scatterers that microcracks are. Certainly, integrated random oriented spheroids instead of spheres in the model will provide theoretical results close to the measured ones.