Geopolymer mesoporosity investigated by intrinsic ionic conductivity using complex impedance spectroscopy
Year: 2026
Type: article
Abstract: The precise characterization of the mesoporous mineral matrix of a geopolymer is greatly complicated by its amorphous nature. No conventional characterization technique allows for its direct investigation. We propose here the use of alternative current impedance spectroscopy (AC-IS; generally called ‘complex impedance spectroscopy’) as an indirect method for probing geopolymers via their ionic conduction properties. Our study of ∼50 K-geopolymer pellets using AC-IS has made it possible to better describe the mesoporosity of alkali-activated materials. The latter were prepared by partial substitution of metakaolin by argillite, and these were then subjected to heat treatment up to 900°C and exposed for a long time to high or low relative humidity. The metakaolin substitution rate along with post-synthesis temperature and storage conditions were the variables that allowed us to track the phenomenon of charge transport via mesoporosity. Refining the impedance spectra over a range of temperatures, using simple and robust models, provided a set of values for the activation energies and diffusion coefficients. The results confirmed the open and ‘through-hole’ nature of the porosity, the localization of K + cations in the interstitial liquid and their diffusion through the amorphous ceramic matrix during heat treatment, as well as the possible resumption of long-term alkaline activation for poorly reactive aluminosilicate sources.
Source: Clay Minerals
Language: English
Subfield: Civil and Structural Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W7124320321
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