Water content imaging during capillary rise within a rammed earth structure

The capillary rise in earthen buildings is a factor of risk since it changes the mechanical properties of rammed earth. A laboratory-scale experiment is performed to see the ability of time-domain induced polarization to non-intrusively monitor the change in the water content during a capillary rise experiment in a rammed earth wall (150 cm in height and 75 cm in width). A total of 64 self-adhesive Ag/AgCl electrodes are placed at the surface of the rammed earth wall. The contact between the electrodes and the wall is insured by a conductive gel. The distance between the electrodes is 4.5 cm. An impedance meter is used to perform time-domain induced polarization measurements at 7 specific dates in July 2022. The raw data (apparent resistivity and chargeability) are inverted to produce tomograms of electrical conductivity and normalized chargeability through the wall. These tomograms are presented along the plane drawn through the position of the electrodes. A petrophysical model recently developed to interpret electrical conductivity and normalized chargeability data is used here to recover the water content distribution over time. The results are compared to local measurements of the water content performed thanks to a TDR (Time Domain Reflectometry) probe placed within the wall. In addition, the wet front associated with the capillary rise is monitored using a camera. The data shows a consistent position of the capillary rise between the various datasets. A methodology is described to obtain the distribution of the water content over space and time in the rammed earth structure.