Quality Of Bricks Produced From Non-Conventional Clays

Abstract

The available information indicated that there is heavy dependence on the sediment of the Nile and its tributaries as well as khours for production of fired clay bricks. About 94% of the produced bricks in Sudan is of Nile sediments origin. This situation led to degradation of highly fertile land. This study aims to find clays suitable for manufacture of bricks away from river banks. One of the most abundant clay type in Sudan, is the black clay which covers about 16% of its area and on which about two third of the population lives. It is widely used as building material that requires special skills and needs continuous maintenance. Black clay of the Khartoum North, the black cotton soil of (Sennar) and kaolinitic clay from Western Omdurman, were chosen to be the alternative clay for production of fired clay bricks. The physical properties (% of sand, clay, silt, pleasticity and shrinkage plastic limit and plasticity index) and its chemical content of (iron, sodium, calcium and potassium) were determined. Thirty bricks from each clay type were manufactured without any treatment or additives. After shaping, drying and firing, the produced bricks were inspected and tested for suitability for use. The results showed that the extent of cracks of the bricks made from the black clay and black cotton clay depends on the method of drying. The bricks kept in dryers showed no cracks. On the other hand all the bricks left to dry in open air cracked. The bricks produced from kaolinitic clay showed no cracks under both drying method. The colour of kaolinitic bricks was whitish. iv After three days of firing, the bricks produced from black clay of black cotton clay was highly broken due to lime-bursting as a result of its lime content. On the other hand the bricks made from kalonitic clay remained intact after firing. The problem of lime-bursting was solved by either grinding the black clay to 1.0 mm or less grain size or by adding common salt (sodium chloride). The results showed the optimum amount of salt is 0.2% by weight. To overcome cracking after firing, different rations of sand and grog were added to the mix. The ideal ratios were: 60% clay, 25% sand and 15% grog for black cotton soil and 70% clay, 10% sand and 10% grog for black soil. To change the kaolinitic bricks from whitish to red colour, materials containing iron oxide were added. The added material included the Blue Nile clay and/or ferruginous stone. The best mix proportion was 70% kaolinitic, 20% Blue Nile clay and 10% grand ferrigunous stone. The study recommended more research to investigate the economic feasibility of these alternatives.