Geopolymers are sustainable structural materials with properties similar to ordinary Portland cement concrete. To better understand the fundamental reaction mechanisms of geopolymers, a microwave materials characterization approach is used. In this research work, the dielectric properties (permittivity and loss factor) of common precursor powders used to make geopolymers (GPPs)—fly ash, lime, metakaolin, silica fume, slag, and zeolite—are measured over the S- and X-band frequency ranges (i.e., 2.0–4.0 GHz and 8.2–12.4 GHz, respectively). The physical characteristics, elemental composition, mineralogical properties, and phase characterization of the GPPs are then correlated to dielectric properties. Permittivity of GPP, classified as pozzolanic or latent hydraulic, is correlated with R 3 calorimetry heat release. Loss factor is correlated with silica dioxide, calcium oxide, and crystalline SiO 2 contents. Powders with less elemental composition diversity tend to exhibit lower permittivity values. Overall, the results reveal novel connections between the dielectric properties and chemical and physical parameters of the GPPs, which may be inputs to advanced characterization studies assessing geopolymer reactivity.
Duong et al. (Fri,) studied this question.