Dehydroxylation Kinetics Of Kaolinite And Montmorillonite Examined Using Isoconversional Methods
Abstract
The use of calcined clays as supplementary cementitious materials (SCMs) in concrete is a promising strategy towards decarbonizing the cement and concrete industry. This is especially relevant considering the ever-increasing demand for concrete. Comprehensive understanding of the kinetics of calcination is essential towards maximizing the potential reactivity of clay minerals while ensuring energy efficiency. In this study, the kinetics of the dehydroxylation of kaolinite and montmorillonite are investigated under non-isothermal conditions at constant heating rate. Activation energies (Ea) are determined via Friedman differential and advanced Vyazovkin incremental methods over the isoconversional range; these are devoid of computational approximations, thus allowing kinetic analysis without assuming a specific reaction model. Kinetic equations—in the differential form as well as a combination of differential and integral forms are compared against the experimentally determined reaction models to identify the most probable dehydroxylation mechanism for kaolinite and montmorillonite. A reaction order mechanism is established for dehydroxylation of kaolinite, while montmorillonite is noted to undergo dehydroxylation via a single-step reversible diffusion-controlled process. Kinetic triplet—comprising activation energy, reaction model and pre-exponential factor—is used to predict isothermal calcination conditions, which is further verified using analytical techniques. Heat release rates of clay-portlandite blends from isothermal calorimetry are used within a thermodynamic framework to quantify reactivity of the calcined clays. The study demonstrates a general approach based on isoconversional methods to predict calcination conditions for different clays that can be used in efficient and optimized production of blended cements or SCMs.
Recommended Citation
O. C. Adesina et al., "Dehydroxylation Kinetics Of Kaolinite And Montmorillonite Examined Using Isoconversional Methods," Applied Clay Science, vol. 270, article no. 107776, Elsevier, Jun 2025.
The definitive version is available at https://doi.org/10.1016/j.clay.2025.107776
Department(s)
Materials Science and Engineering
Second Department
Civil, Architectural and Environmental Engineering
Keywords and Phrases
Dehydroxylation; Kaolinite; Kinetics; Montmorillonite; Reactivity; SCM; Thermogravimetric analysis
International Standard Serial Number (ISSN)
0169-1317
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2025 Elsevier, All rights reserved.
Publication Date
15 Jun 2025
Comments
Arizona State University, Grant DMR 2228782