Influence of the size and frequency of contact transducers on the determination of concrete permeability by ultrasonic velocity and attenuation

In this paper we prospected the possibility of estimating air and water permeability of concretes by indirect UPV and attenuation, this is for the purpose of substituting the destructive permeability tests realized on cores levied on the structure to auscultated by non-destructive tests in-situ. This study showed an increase in permeabilities with the increase in the W/C ratio. The curing in water affects positively the permeabilities and the correlations of indirect UPV with permeability and attenuation with permeability. The increase of both permeabilities in both curing modes shows a decrease in indirect UPV and an increase in attenuation, this is observed by the various transducers used (d , D, D , d). The correlations between indirect UPV, attenuation and permeability are linear. Changes in velocity are more visible in low permeability concretes, but attenuation is more affected by permeable concretes, this is justified by the changes in the microstructure of the concrete with the W/C ratio. Decreasing in the reflection angle of the transducers improves the correlation between indirect UPV, attenuation and permeability. The increase in the diameter of the transducers improves the correlations between UPV and permeability, and has led to a decrease in correlations between attenuation and permeability, it can be explained by the divergence of the reflection angle (λD=0.2λd). The increase in the frequency affects negatively the quality of the attenuation/permeability correlation and does not have an important influence on the improvement of the velocity/permeability correlation; this requires a more in-depth analysis for the obtained signals and the microstructure of concrete.