Thesis defense of Marie-Ange EID
Marie-Ange EID, PhD student at Lames, Université Gustave Eiffel, has defended her thesis entitled
"Monitoring of concrete electrical properties by embedded resistivity sensors, for the modelling of the hydric and ionic transport phenomena encountered during marine tide"
on
thursday november 7th 2024
at 2.00 PM at the amphitheatre of Université Gustave Eiffel, campus of Nantes (France)
| Reporters: Matthieu BRIFFAUT Cyrille FAUCHARD | Professeur, Ecole Centrale de Lille Directeur de Recherche - HDR - Cerema |
| Examinators: Jean-François LATASTE Fabrice DEBY Béatrice YVEN | Professeur, Université de Bordeaux Maitre de Conférences - HDR - Université Paul Sabatier, Toulouse Docteur, ANDRA |
| Thesis directors: Géraldine VILLAIN, director Stéphanie BONNET, co-director | Ingénieur Divisionnaire des TPE - HDR - Université Gustave Eiffel, Nantes Professeur, Nantes Université |
| Supervisor: Sérgio PALMA LOPES | Ingénieur Divisionnaire des TPE - Université Gustave Eiffel, Nantes |
Abstract:
This thesis is conducted within the "ANR-DEMCOM" project, which focuses particularly on maritime structures exposed to chloride penetration from seawater. This phenomenon can lead to the corrosion of steel reinforcements, resulting in the deterioration of the structure. Therefore, it is crucial to establish a monitoring method necessary for a reliable diagnosis, especially in inaccessible areas such as the tidal zone. The objective of this thesis is to use embedded resistivity sensors to determine water and chloride content profiles. The embedded sensor allows for monitoring the evolution of the concrete’s electrical resistivity over time and over the entire thickness of the structure. Due to the distribution of electrodes along the sensor, the apparent resistivity measurements obtained are considered a good estimation of the true resistivity of the material. As a result, no inversion process is needed, unlike resistivity measurements obtained by the surface techniques. The experimental study is conducted on concretes formulated with blast-furnace slag, a mineral addition known for its positive effects on the transport properties of concrete. Instrumented specimens are subjected to a diffusion campaign (under saturated conditions), to an imbibition campaign and tidal cycles (under unsaturated conditions), in order to separate water from chlorides. The resistivity profiles are converted to saturation degree and chloride profiles, using calibration curves and calibration surfaces established for each concrete. The obtained experimental profiles are then used to estimate durability indicators, namely water permeability and chloride diffusion coefficient, by fitting a transport model to the experimental data. The chosen model is based on a thermodynamic approach that describes moisture transfer through the movement of the liquid and gaseous phases in porous media. The use of this model requires the knowledge of numerous input parameters, leading to the adoption of certain assumptions and simplifications previously proposed in the literature.
Keywords: monitoring, electrical resistivity, slag, water and chloride content