Mechanical activation and geopolymerisation of Taiwanese fly ash
DOI:
https://doi.org/10.17794/rgn.2025.5.12Keywords:
fly ash, geopolymer, mechanical activation, pozzolanic activityAbstract
The use of raw fly ash in the production of cement and geopolymer products is limited due to its low reactivity. However, the reactivity of fly ash can be increased through a mechanical activation process, allowing for its wider use. This study focused on the mechanical activation and geopolymerisation of coal fly ash originating from Taiwan. The mechanical activation was carried out by grinding in a batch-stirred media mill for 1, 3 and 5 minutes. The fineness and specific surface area significantly increased after 1 minute, and then only slightly decreased with further milling. The lime absorbance test showed significant improvement in pozzolanic activity (130-140% increase) after mechanical activation. For geopolymer synthesis, a 10M NaOH solution was used as an alkali activator with a liquid/solid ratio of 0.35. The geopolymer containing 3-minute fly ash grind produced the highest 28-day compressive strengths (36.1 MPa). The structural characterisation of fly ash and geopolymer was carried out by Fourier Transform Infrared (FTIR) spectroscopy. Changes in the FTIR spectra of fly ashes indicated the formation of amorphous aluminosilicate gel, a new reactive product as a result of geopolymerisation. Based on the strength development of geopolymers, mechanical activation enhanced the reactivity of fly ash, resulting in rapid setting and higher strength development during the early stages of geopolymerisation. The results clearly showed that, after mechanical activation, fly ash became a more reactive raw material, offering greater application potential than its current uses in cement production, road construction, and soil stabilisation.
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Copyright (c) 2025 Fanni Dolgos, Roland Szabó, Wei-Ting Lin, Gábor Mucsi
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