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Abstract In this paper, the effects of two alkaline activators, water glass and sodium hydroxide, on the alkali activation behavior of fly ash were studied. The viscosity changes of the system and the dissolution behavior of Si4+ and Al3+ ions in the liquid phase were tested. The phase composition, morphology, and reactant bonds of hydration products in the hardened paste were studied by XRD, SEM, and infrared spectroscopy. The results show that the alkalinity of NaOH solution is higher, the degree of corrosion on the surface of fly ash is more serious, and the dissolution efficiency of Al3+ and Si4+ is higher. In the alkaline environment, the dissolved ions reach the saturation degree of silicon and aluminum monomers, and polymerize to form aluminosilicate oligomer, and then form N-A-S-H gel. Water glass has a corrosion phenomenon on fly ash particles, and then the dissolved Al3+ and Si4+ undergo geopolymerization to form N-A-S-H gel. The scanning electron microscopes revealed that with the extension of reaction time, the surface of fly ash was wrapped with N-A-S-H gelatinous material, and become increasingly dense.
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Published: 01 September 2025
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2025, Vol. 0 
