Title:
Dehydroxylation Kinetics of Kaolinite and Montmorillonite Examined Using Isoconversional Methods
Author(s):
Neithalath
Publication:
Web Session
Volume:
ws_S25_Neithalath.pdf
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
3/30/2025
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. In this study, the kinetics of the dehydroxylation of pure kaolinite and montmorillonite are investigated under non-isothermal conditions at constant heating rate. Activation energies ( ) are determined via Friedman differential and advanced Vyazovkin incremental methods for the isoconversional range; these are devoid of computational approximations. 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. An 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-CH 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.