Detection of chemical damage in concrete using ultrasound.
This research deals with a non-destructive method for characterizing the degraded cover of concrete structures using high-frequency ultrasound (0.5-1 MHz). Although such a frequency range is unusual in civil engineering, it is well suited to the kind of defect to be detected, as it corresponds to a thin near-to-surface layer with increased porosity and density of microcracks. In order to assess the feasibility of detecting concrete cover degradation, velocity and attenuation measurements were made on both halves of a concrete slab. One half was immersed into an acid solution for 15-45 days, while the other half remained sound. These measurements were made for longitudinal, transverse and surface waves. The results obtained show a 23% decrease of ultrasonic pulse velocity and a 1000% increase of attenuation in the degraded material relative to the sound material. It is thus possible to detect and characterize concrete cover degradation using high-frequency ultrasound. Although attenuation measurements in heterogeneous media are difficult, their sensitivity to degradation is very high.
Ould Naffa
S
S
Electronics and Acoustics Group, IEMN DOAE UMR CNRS 8520, Ecole Centrale de Lille, Villeneuve d'Ascq, France. sidi.ouldnaffa@ec-lille.fr
Goueygou
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M
Piwakowski
B
B
Buyle-Bodin
F
F