Propagation and diffusion in very heterogeneous media

The theme "Multi-physical characterization of materials" aims to link non-destructive (ND) or geophysical observables to indicators or state parameters of the materials being assessed. Unlike the other two themes, it does not focus on geometric issues. The materials studied are mainly construction materials (concretes and bituminous asphalt) and soils (natural or treated). For these materials, estimating porosity, water content, chloride content, and micro-cracking are the main challenges to be addressed for a more quantitative assessment and monitoring and optimized management of structures.
Continuing the actions from the theme "Propagation and diffusion in complex media" of the previous scientific project, several challenges arise, particularly for concrete. One of them concerns the decoupling of the sought parameters, such as water content and chloride content. Another addresses environmental biases (temperature, ambient humidity, vibrations, etc.) during signal processing and analysis. A third develops the use of the non-linear properties of ultrasound (US) propagation for their significant sensitivity to certain pathologies (e.g., carbonation). To meet these challenges, multi-physical approaches, already present in some ongoing or completed projects, are becoming essential. Various information processing strategies are being considered, such as transferring the methodology for merging geophysical and geotechnical data to the fusion of non-destructive testing (NDT) measurements and destructive measurements applied to asphalt concrete, the joint inversion of complementary physical data, or the use of artificial intelligence techniques, already employed through collaborations and of growing interest and attention within the team. In the long term, these approaches could be integrated into digital twins of the studied objects through collaborations.