Characterization of Gula Clay for Refractory Applications

Abstract

This study evaluates the physical, thermal, chemical, mineralogical, and microstructural characteristics of raw clay sampled from Gula town in the Biu Local Government Area of Borno State, Nigeria, to determine its suitability as a local alternative for industrial refractory applications. The clay sample was processed and subjected to standardized testing profiles including apparent porosity, bulk density, moisture content, firing shrinkage, loss on ignition (LOI), thermal shock resistance, and cold crushing strength (CCS). Chemical and mineralogical compositions were determined using X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS). The results showed that Gula clay satisfies the specifications for a standard fireclay. The evaluation physical and mechanical properties revealed an apparent porosity of 23.02%, a bulk density of 1.88 g/cm³, a moisture content of 4.06%, and a low firing shrinkage of 7.2%, which minimizes the risk of structural warping. Mechanically, the clay exhibited a high CCS of 26.52 MPa and an excellent thermal shock resistance of 26 cycles, confirming its ability to withstand acute thermal stresses in high-temperature environments. XRF analysis indicated major oxide concentrations of SiO₂ (55.24%) and Al₂ O₃ (22.72%), while qualitative XRD analysis confirmed quartz (55.14.0%) and orthoclase feldspar (34.0%) as the dominant primary mineral phases, alongside minor fractions of goethite and anorthite. SEM/EDS microstructural analysis revealed highly dispersed, non-spherical particles with tight intergranular bonding and Mg was detected at approximately 4.0 wt.% in the analyzed EDS region, although Mg was not significant in the bulk XRF composition. Collectively, these results establish that Gula clay possesses the required thermomechanical and chemical benchmarks to serve as a viable, low-cost local substitute for imported siliceous fireclay refractory materials in industrial refractory applications.