Assessment of the Egyptian clay deposits for ceramic industries: a review paper

Abstract

The nature as well as composition of the Egyptian clay deposits exposed all over the country are summarized. The influence of composition on their ceramic properties in terms of plasticity as well as drying and firing behaviour is discussed. According to their clay mineral composition, they are classified into kaolinite-, smectite- and illite- rich clays. The kaolinite rich clays are mainly exposed in Aswan as well as Gulf of Suez provinces and generally characterized by a slow rate of slaking in water, low plasticity, high Al₂O₃ as well as a high and long vitrification range (1100-1500 °C). Hence, they are used in the production of shaped and unshaped refractories as well as vitreous china and white Portland cement. However, they are not suitable for the production of white wares due to their high colouring iron and titanium oxides content. On the other hand, smectiterich clays cover most of the Eastern as well as Western Deserts and have low Al₂O₃ content with variable amounts of quartz, calcite, gypsum and iron minerals as well as alkali water-soluble salts. They show high plasticity, drying and firing shrinkage as well as a low and short vitrification range (850-1000 °C). Therefore, they are applied for the production of ordinary Portland cement and building bricks. Also, they are recommended for the manufacture of light-weight clay aggregate due to their bloating on firing up to 1250 °C. Meanwhile, illite-rich clays are encountered in El-Bahariya Oasis, Western Desert and contain predominant iron-rich illite clay minerals, i.e. glauconite in addition to variable amounts of kaolinite, smectite, quartz and goethite minerals. They have moderate plasticity, vitrification range (950-1150 °C) as well as drying and firing shrinkage. Hence, they are recommended for manufacturing building bricks and other heavy-clay products, after blending their varieties.