CHEMICAL ANALYSIS OF RAW MATERIALS AND FLY ASH FOR REFRACTORIES

Abstract

This study aims to investigate the chemical composition, phase transformations, and microstructural characteristics of natural clay and fly ash from a thermal power plant (TPP) for their combined use in refractory materials, with a focus on compatibility within an aluminosilicate matrix and its influence on material performance. The chemical composition of raw materials was determined using X-ray fluorescence spectroscopy (XRF). Phase composition and high-temperature transformations were analyzed by X-ray diffraction (XRD). Microstructural features, particle morphology, and elemental distribution were examined using scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS). Comparative analysis of major oxides (SiO₂, Al₂O₃, Fe₂O₃, TiO₂) was conducted across all samples. The results show that fly ash consists of fine, predominantly spherical aluminosilicate particles that enhance packing density and reactivity. Its incorporation into the clay matrix promotes intensified mullite formation during heat treatment due to increased availability of reactive silica and alumina. XRD analysis confirmed the formation of primary and secondary mullite phases, while the presence of alkali oxides in fly ash influenced glass phase formation and accelerated phase transformations in the contact zone between clay and ash particles. SEM observations revealed improved microstructural homogeneity and reduced porosity in the modified compositions. The integration of fly ash as a partial substitute for natural clay improves phase development, enhances microstructural properties, and reduces raw material consumption. The findings confirm the potential of utilizing industrial waste in refractory production, contributing to resource-efficient technologies and advancing sustainable practices within green chemistry and industrial ecology.