Non-contact, automated surface wave measurements for the mechanical characterisation of concrete

This paper presents two automated devices for conducting non-contact ultrasonic measurements (with air coupling and laser interferometry) for the purpose of recovering mechanical properties (porosity) on a series of concrete slabs using surface waves. The devices employed herein as part of an extensive laboratory experimental campaign are also intended to be operational onsite. The ultrasonic frequencies applied lie in the range of 40–300 kHz; moreover, according to surface wave (SW) properties, the investigation depth of a few centimetres corresponds to the cover concrete investigation target. The measurements of SW velocity and attenuation are described and used to characterise various concrete mixes. The efficiency of such measurement devices is demonstrated, within the scope of the French research project SENSO, by means of laboratory measurements carried out on manufactured cement slabs.