# Influence of moisture on the estimation of nonlinear parameters in concrete with Nonlinear ultrasonic Coda Wave Interferometry

Speaker:
Abraham, Odile; IFSTTAR Departement Geotechnique environnement risques naturels et sciences de la terre; France

Authors:
Legland, J.-B.; IFSTTAR; France
Théry, R .; IFSTTAR; France
Abraham, O.; IFSTTAR; France
Villain, G.; IFSTTAR; France
Durand, O.; IFSTTAR; France
Larose, E.; ISTERRE; France
Tournat, V.; LUNAM University; France

ID: ECNDT-0442-2018
Session: Nonlinear Ultrasonics 2
Room: G2
Date: 2018-06-12
Time: 13:30 - 13:50

Experiments dedicated to the condition assessment of concrete under stress (Zhang et al., 2012, Legland et al., 2017a), crack sizing (Hilloulin et al., 2014, Zhang et al., 2017) and crack healing monitoring (Hilloulin et al., 2016) have shown that Nonlinear ultrasonic Coda Wave Interferometry (NCWI) is a very sensitive technique that can be used in the lab as well as in the field (Legland et al., 2017b).
This technique belongs to the family of nonlinear techniques that uses pump-probe experimental set-ups. The probe wave is the coda wave (in a frequency range where the wavelengths are smaller than the average aggregate size, typically above 200 kHz, and can propagate to decimeter distances, typically below 800 kHz). The pump wave is a high amplitude low frequency sweep chosen to insonify uniformly the sample under (typically below 50 kHz).
The nonlinear acoustic behavior observed in concrete is linked to the interface between aggregate and mortar, micro-cracks, porosity, etc. In this paper we try to quantify and explain the role and influence of moisture when attempting to quantify the hysteretic non classic nonlinear acoustic parameters measured by NCWI.
An experiment on a slab in a controlled environment with permanent monitoring of moisture content is conducted during several hours while water propagates inside the sample. In this paper the repeatability of the experiment is demonstrated and the diminution of the value of the acoustic nonlinear parameters with water ingress is quantified.

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