Mineralogy and physic-chemical characteristics of indurated shale quarry waste and influence of firing temperature on their ceramic properties for incorporation in production of roofing tile

Abstract

Quarry wastes from indurated shales with huge reserves across Abakaliki, Southeastern Nigeria were evaluated for use as raw materials in manufacturing of roofing tile. Firstly, the indurated shales were investigated by their mineralogical (X-ray diffraction, XRD), chemical (X-ray fluorescence) and physical (grain size distribution and Atterberg limits) characteristics. As technologies of building-related ceramic production involved firing to varying temperatures, ISQW samples were fired to determine their technological properties (linear shrinkage, weight loss, water absorption, bulk density and flexural strength). From the results, ISQWs composed predominately of fine particles (clayey-silt) with medium plasticity. The XRD revealed predominance of illite-chlorite-vermiculite with high contents of quartz and variable percentage of carbonate and feldspar. The oxides were dominated by SiO2 and Al2O3, low contents of ferromagnesian elements with considerable amounts of alkali (K2O and Na2O) which can act as fluxes and may have effect during sintering. The CaO concentrations are variable and relate to carbonate contents. Characterizations based on compositional ternary, clay workability chart and Winkler diagrams revealed their acceptable level for ceramic applications. The Winkler and McNally diagrams revealed heterogeneous behaviors as the samples fell within vertical corrugated bricks, perforated products and tiles production. The ISQWs fired at 1000oC revealed considerable weight loss, linear shrinkage and water absorption with unsatisfactory performance for flexural strength. Flexural strength increased as firing temperature increased due to the formation of dense phase. Beneficiation of ISQWs in order to achieve excellent properties and reduce sintering temperature for their usability in production of roofing tiles is recommended.