Impedance Spectroscopy as a Methodology to Evaluate the Reactivity of Metakaolin Based Geopolymers
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Data
2022-11-25
Autores
Sanches, Alex Otávio
Istuque, Danilo Bordan
Bortoletto, Marcelo
Malmonge, José Antônio
Soriano, Lourdes
Borrachero, María Victoria
Payá, Jordi
Tashima, Mauro M.
Akasaki, Jorge Luis
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MPDI
Resumo
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 MKbased
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.
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Palavras-chave
Geopolymer, Metakaolin, Impedance spectroscopy