Imaging of a water front progression in concrete, using coda wave interferometry

Thery, Romain; IFSTTAR Departement Geotechnique environnement risques naturels et sciences de la terre; France

Thery, R.; IFSTTAR; France
Legland, J.-B.; IFSTTAR; France
Abraham, O.; IFSTTAR; France
Durand, O.; IFSTTAR; France
Villian, G.; IFSTTAR; France
Larose, E.; ISTERRE; France

ID: ECNDT-0405-2018
Download: PDF
Session: Civil Infrastructure-Conrete 2
Room: J1
Date: 2018-06-13
Time: 11:30 - 11:50

Determining water content in concrete is an important issue in civil engineering, as water is responsible for many damages in this material. Electro-magnetic non destructive methods are usually used to assess this water content. However, due to the ionic content and the complexity of the material, this quantity is difficult to estimate, and complementary acoustic techniques would present a great improvement. In this work we exploit the heterogeneous nature of our medium by using coda waves and its greater sensibility to changes in the materials, to experimentally observe the progression of a water front ascending by capillarity in a concrete bloc.
Based on records of coda waves propagating through the medium before and during the progression of the water, Coda Wave Interferometry techniques allows us to extract two quantities. These are the velocity variation of the coda waves and their decorrelation, which are respectively related to strain and structural changes, both sensitive to water presence. To interpret this as the expression of local changes, we use the Locadiff technique. This method offers a direct model that interprets, using sensitiviy kernels, these quantities as the weighted sum of the contributions of all the local changes in the material. We here present the results of this study and confirm them thanks to humidity sensors placed in the concrete bloc.