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.
The present study describes research carried out to evaluate the mineralogical, geochemical and technological properties of indurated shale-quarry wastes and assess the suitability of these low-cost and locally available quarry wastes generated from crushed indurated shales for possible use as alternatives to fresh raw materials in the manufacture of roofing-tile products. Firstly, the mineralogical and chemical properties of the indurated shales were investigated by X-ray diffraction (XRD) and X-ray fluorescence, while their physical properties were identified by grain-size distribution, Atterberg limits, and clay activity. Samples of indurated shale-quarry wastes (ISQWs) were subjected to heat treatment at elevated firing temperatures to provide the required strength and durability and their ceramics properties (linear shrinkage, weight loss, water absorption, bulk density, and flexural strength) were determined. From the results, the ISQWs were composed predominantly of fine particles with medium plasticity and clay activity with values generally >0.75. The mineralogy revealed a predominance of aluminosilicates (illite-kaolinite-smectite-chlorite) with large quartz contents and variable percentages of carbonate and feldspar. The oxides were dominated by SiO2 and Al2O3, small amounts of ferromagnesian minerals, and considerable amounts of alkalis (K2O and Na2O) which act as fluxes. The CaO concentrations were variable and related to carbonate contents. Characterizations based on compositional ternary (total clay mineral-carbonate-quartz + feldspar) systems, Casagrande clay workability charts, and Winkler and McNally diagrams revealed their suitability for ceramics applications as the majority of ISQW samples fell within the specifications for roofing tiles. The ISQWs fired at a high temperature of 1000°C revealed considerable weight loss, reduction in both linear shrinkage and water absorption with insignificant increase in flexural strength. In order to achieve excellent ceramics properties and further reduce sintering temperature for their suitability as raw materials in the production of roofing tiles, beneficiations of ISQWs are highly recommended.
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