"Dehydroxylation Kinetics Of Kaolinite And Montmorillonite Examined Usi" by Oluwadamilare Charles Adesina, Sayee Srikarah Volaity et al.
 

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.

Department(s)

Materials Science and Engineering

Second Department

Civil, Architectural and Environmental Engineering

Comments

Arizona State University, Grant DMR 2228782

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

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