Multiscale Modeling of the Dielectric Response of C-S-H

The interpretation of dielectric measurements in cement-based materials, as well as multiscale modeling strategies, requires the knowledge of the intrinsic permittivity of their various constituent phases. Calcium silicate hydrates (C-S-H) is the major hydrated phase in concrete (when clinker is the main cement compound), but to date, its frequency-dependent complex dielectric response remains unknown. Direct experimental measurements of C-S-H intrinsic dielectric behavior are challenging due to the scales to be probed and the difficulties in isolating this component in cement systems. Molecular simulations arise as a helpful tool to provide reliable estimates of properties bottom-up. This study adopts a multiscale approach to estimate the complex dielectric response of C-S-H over a frequency range of [0; 100 GHz]. We perform molecular dynamics simulations to compute the frequency-dependent dielectric response of water in C-S-H using theoretical framework of Statistical Physics, which enables us to associate the microscopic decay in water polarization correlations to the dielectric response. Several configurations are considered by varying the interlayer distance, covering the range of pore sizes associated with interlayer pores and gel pores in C-S-H. The dielectric response is anisotropic and pore size dependent, as expected in layered materials. The results at the molecular scale are then used as inputs in a homogenization model to estimate the dielectric permittivity of C-S-H gel, which we compare with estimations obtained from inverse analysis based on Micromechanics. Our results are a valuable input for multiscale modeling of non-destructive testing and evaluation in cement-based materials.