Thermal Transformation of Kaolinite Clays: Analyzing Dehydroxylation and Amorphization for Improved Pozzolanic Performance
Khaled Azizi, Jabrane Maissara, M. ELMAHI CHBIHI, Youssef Naimi
Abstract
This study explores the impact of heat treatment parameters on the dehydroxylation and amorphization processes of kaolinite-based materials, in particular natural kaolin clays. It develops a quantitative method for estimating the amorphous phase in heat-treated kaolinite, using differential thermal analysis/thermogravimetry (DTA/TGA), mass spectrometry, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Kaolin clays, subjected to controlled heat treatments between 600°C and 800°C, undergo significant structural transformations. The study identifies the degree of dehydroxylation (DTG) as a crucial measure of kaolinite performance after heat treatment, calculated as a function of sample weight loss. The transition from a crystalline to an amorphous phase strongly influences pozzolanic activity, characterized by its ability to react with portlandite (Ca(OH)₂) in water-rich environments.The materials used, including clay from the Benslimane region of Morocco, were finely ground and subjected to various thermal treatments. Thermal analyses revealed characteristic patterns of mass loss and phase transformation. XRD and FTIR analyses provided detailed information on structural changes, confirming the amorphization of kaolinite after dehydro.