Permittivity measurement of cementitious materials and constituents with an open-ended coaxial probe: combination of experimental data, numerical modelling and a capacitive model

Abstract

The study presents the development of a new two-dimensional FEM numerical model describing the operation of two large open-ended coaxial probes designed to investigate the permittivity of concrete, and its constituents. This numerical simulation, combined with a capacitive approach describing the behaviour of the probes, enabled to prove the suitability of such device to determine the permittivity of dispersive dielectrics. Finding back the permittivity of a specified material by calculation of the S parameters, change of the reference plane and use of the capacitive model is the key to the proof. Measurements performed onto different materials show good similarities with the numerical simulations. Special considerations are mentioned concerning the size of the probe and its ability to measure the permittivity of heterogeneous materials made of large inclusions. Combination of such numerical tool and measuring device can be used as a non-destructive testing technique to assess the near surface permittivity of concrete structures or as a calibration technique for GPR measurements.

Dielectric properties of the pore solution in cement-based materials

“…a Debye-like behavior) than the values of late ages solutions (PC5-PC7). In agreement with our results, recent experimental measurements of the dielectric response of a concrete pore solution show that the real part remains almost constant for frequencies up, at least, to 2 GHz [54]. The same authors also showed that a Debye model can describe fairly well the dielectric spectra of the pore solution, which is also consistent with our results that show values of α close to zero.…”

Electromagnetic Properties of Concrete: Bottom-Up Modeling from the Molecular Scale

“…Figure 4 shows the effective frequency-dependent dielectric spectra at cement paste, mortar, and concrete scales. We considered a dielectric permittivity of solids of 8 based on experimental evidence from the literature [3]. The real part of the dielectric permittivity decreases with age for frequencies below 0.05 GHz and slightly increases with age for higher frequencies.…”

“…We assumed a volume fraction of sand at the mortar scale of 40% and of coarse aggregate at the concrete scale of 40%. We considered a dielectric permittivity of solids of 8 [3].…”

Machine learning and micromechanics as allies to establish composition-property correlations in cement pastes

“…MB modeling has been successfully used to unveil CompositionśProperty correlations for various properties in cement-based materials, including mechanical (Wyrzykowski et al 2017;Pichler and Hellmich 2011;Sanahuja et al 2007;Königsberger et al 2021), transport and thermal (Bary and Béjaoui 2006;Patel et al 2016;Honório et al 2018a), and electromagnetic (Guihard et al 2019;Honório et al 2020b;Honório et al 2020a) properties, as well as coupling properties in the thermo-poro-mechanical framework (Ulm et al 2004;Ghabezloo et al 2009;Honório et al 2018a;Honório et al 2018b). An advantage of MB modeling is the simplicity of computations, which enables assessing various scenarios of interest regarding the composition, uncertainty on phase properties (Honório et al 2020b), and morphology of phases in a heterogeneous material.…”