Impedance Spectroscopy as a Methodology to Evaluate the Reactivity of Metakaolin Based Geopolymers
Abstract: The aim of this study was to use the electrical impedance spectroscopy technique (IS) to carry out a systematic study on the mechanism of metakaolin geopolymerization for up to 7 curing days. The study was developed on two batches of metakaolin (MK), and their reaction processes were compared. Interpretative fundamental elements were developed based on the effective electrical conductivity curves regarding the metakaolin geopolymerization. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were previously carried out and used to interpret and validate the electrical behavior of the fresh and hardened MK-based geopolymer pastes. The results highlighted the sensibility of the impedance technique to the identification and description of the MK geopolymerization process, as well as the changes resulting from even slight variations in the metakaolin composition. Furthermore, this indicated that the geopolymerization process in highly alkaline solutions could be divided into seven stages, including the processes of dissolution, nucleation, precipitation and formation of the gel and, eventually, the retraction/microcracks constitution. Late dissolution processes could be observed during the more advanced stages and were attributed to particles not being fully hydrated.
Author(s): Bordan Istuque, D.; Sanches, A. O.; Bortoletto, M.; Malmonge, J. A.; Soriano, L.; Victoria Borrachero, M.; Paya, J.; Tashima, M. M.; Luis Akasaki, J.
Materials
Published: 25 November 2022
DOI: https://doi.org/10.3390/ma15238387
CDMF
The CDMF, hosted at the Federal University of São Carlos (UFSCar), is one of the Research, Innovation and Dissemination Centers (RIDC) supported by the São Paulo State Research Support Foundation (Fapesp), and also receives investment from the National Council Scientific and Technological Development (CNPq), from the National Institute of Science and Technology of Materials in Nanotechnology (INCTMN).
