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Open AccessArticle

A Kinetic Study of the Pozzolanic Reaction of Fly Ash, CaO, and Na2O in the Preparation of Fly Ash Belite Cement

1
Departments of Civil Science and Engineering, University of Yangzhou, Yangzhou 225127, China
2
College of Mechanics and Materials, University of Hohai, Nanjing 210098, China
3
Departments of Building Engineering, University of Yangzhou Polytechnic, Yangzhou 225009, China
*
Authors to whom correspondence should be addressed.
Materials 2019, 12(20), 3303; https://doi.org/10.3390/ma12203303 (registering DOI)
Received: 16 September 2019 / Revised: 5 October 2019 / Accepted: 9 October 2019 / Published: 11 October 2019
(This article belongs to the Special Issue Ceramics and Construction Materials)
Fly ash belite cement is a kind of low-carbon cement prepared by a two-step process involving hydrothermal synthesis and low-temperature calcination. Pozzolanic reaction pastes, as the precursors of fly ash belite cement prepared by hydrothermal synthesis, are affected mainly by reaction temperature, time, ratios of the mass of fly ash/lime (FA/CA), and the dosage of Na2O. The absorbance rate of CaO with reaction time was tested for all samples, and the reaction kinetic model and parameters of the granule-hydrothermal synthesis method were discussed. A kinetic model for the hydrothermal synthesis in the presence of Na2O was proposed based on the Kondo’s modified Jander equation and Arrhenius equation. The activation energy (Ea) of the process was determined to be 67.76 kJ/mol. In addition, with an increasing dosage of Na2O, the pre-exponential factor A of the Arrhenius equation increased. However, the hydrothermal reaction degree was accurately predicted using the kinetic model characterized by the absorption rate of CaO. The results indicated that Na2O, as an alkali activator, facilitated the diffusion of Ca2+ firstly, then partly dissolved the amorphous phase in the mixtures and, finally, accelerated the formation of poorly crystallized hydrates. View Full-Text
Keywords: low activity; fly ash; belite cement; hydrothermal reaction; NaOH; kinetic model low activity; fly ash; belite cement; hydrothermal reaction; NaOH; kinetic model
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Gong, Y.; Yu, B.; Fang, Y.; Yang, D.; Wu, S.-A.; Yan, Y. A Kinetic Study of the Pozzolanic Reaction of Fly Ash, CaO, and Na2O in the Preparation of Fly Ash Belite Cement. Materials 2019, 12, 3303.

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