EIS investigation on electrical properties of metakaolin-based geopolymer

This study investigates the effects of water loss and temperature on the electrical properties of metakaolin-based geopolymer (MKG) using electrochemical impedance spectroscopy (EIS). The results show that the electrical behaviour of MKG involves two processes during water loss: the charged ions exhibited Warburg diffusion behaviour in the pore solution (slow process) and the non-ideal diffusion behaviour of charged ions at the geopolymer/electrode interface (fast process). As the water loss increases, the electrical conductivity mechanism changes from the slow process dominant to the fast process dominant. The slow process of dried MKG is mainly influenced by temperature. Dried MKG with low water/binder (w/b) ratio shows increased conductivity with temperature, while MKG with high w/b ratio maintains stable conductivity. A conductive mechanism indicates that the small pore of MKG with low w/b ratio has difficulty in removing water. At high temperature, the enhanced mobility of ions allows them to move through the remaining pore solution network, resulting in reduced impedance.