Experimental characterization of two clay deposits blended with feldspar and quartz for building services and refractory applications

Clay deposits across the globe have variations in mineralogical compositions that elicit their use in numerous applications. In this study, two clay deposits were identified and blended with feldspar and quartz in various amounts to produce different samples of composites that could be used for applications in building services and refractories. Chemical analysis, mineralogical composition, microstructure, physical properties, and thermal behaviours were characterized. The X-ray fluorescence (XRF) analysis results show that the clays belong to the aluminosilicate group containing traces of other oxides which enhance strength and the crystallization of thermally stable phases. The XRD patterns confirmed the presence of dominant quartz with moderate to minor presence of kaolin, orthoclase, and albite. The texture of the clays showed particles of different sizes and shapes with uneven distribution. The EDX characteristic spectrum showed x-ray characteristic peaks of Si, Al, Fe, K, and O which affirmed their major oxide compositions. Physical properties results show that firing at various temperatures and blending resulted to increase in Bulk density and flexural strength while apparent porosity and water absorption decreased. The TGA, DTA, and DSC results show that the two clay minerals are thermally stable. This can be attributed to the nucleation and crystallization of refractory phases like cristobalite and mullite. Addition of feldspar and quartz was found to contribute significantly to improve the overall properties of the investigated clays. A comparison of the various results from the two clay deposits suggests that they could be suitable for building services and refractory applications.