Laboratory study of the electrical properties of Lutetian limestones in the 100 Hz to 10 MHz frequency range

Abstract

ABSTRACTLutetian limestones have been widely used in historical monuments within the Paris Basin during the course of the medieval and modern periods. Among the physical properties that can be used to assess the evolution of the limestonesin situin the buildings and their present health, the complex effective permittivity in the 10–100 kHz frequency range is easy to measure and reflects the internal structure of the stone along with the dependence on the water content. To improve our knowledge about this property, a laboratory study on four samples collected in the relevant quarries has been undertaken using measurements in the 100 Hz–10 MHz frequency range. Except close to zero water content, the observed results exhibit a quasi‐absence of variation of the real effective permittivity with the water content. The frequency variation fits fairly well with a model taking into account a Jonscher's decrease, a direct current conductivity, a high‐frequency dielectric permittivity and losses, and a relaxation phenomenon. When fitted by a Cole–Cole model, the magnitude of the corresponding relative permittivity change always stays close to 30, but the time constant varies from 1.0 μs to 0.1 μs as the water content increases.