Implications and characterization of waste glass cullet – kaolinite clay ceramics

Abstract

Cullet(x) reinforced ceramics (100 – x) made from Ukpor kaolinite clay by dry-pressing and fired at temperatures (T⁰C) for 900≥T≤ 1250⁰C with 0≤x ≤40% wt was investigated for its ceramics application. The chemical profile of the samples (cullet and clay) was determined by Atomic Absorption Spectroscopy (A.A.S) technique. Mineral composition was determined by XRD while SEM was employed to view the phase modification. The particle size of the raw materials was maintained at <180μm. The mechanical properties, micro-structure, and phase composition are discussed with respect to cullet content and temperature variation. It was observed that production temperature decreased with increase in cullet. Micro-structural study showed a granulated morphology and the formation of phase-boundary as granules fuse due to clay cullet crystallization with increase in cullet and temperature. Electrical insulation is greatly improved while thermal insulation is reduced due to the closure of pores with increase in cullet and temperature respectively. The mechanical properties of flexural strength, porosity, bulk and apparent density, shrinkage and water absorption were greatly modified for every 10% increase in cullet content. Production temperature greatly reduced with increase in cullet suggesting longer lifespan for the kilns and furnaces used. The study supports the utilization of cullet in the production of ceramics, a good reason to recycle waste to wealth but in excess of 20% cullet, production temperature must not exceed 1100⁰C due to development of cracks.

Keywords: Bulk Density, cullet; porcelain; porosity; Ukpor clay (U.C); temperature