Development of quality control plan for Uganda local clay bricks manufacturing industry to achieve durability for local clay bricks.

Abstract

Clays occur widely in many parts of Uganda. Besides their geological interest, they are of importance for the local industry. They have been used to produce rather poor quality bricks, tiles and pottery by primitive methods for several years. Scattered clay pits and brick kilns along the roadsides document the uncontrolled and low-technology exploitation of the Uganda clay occurrences. Apart from artisan brick producers, there are organized clay works, such as Uganda Clays at Kajjansi, and Nkozi Clays along the Masaka road, which supply the construction industry in Kampala and surroundings. The fore mentioned industries cannot meet the ever-increasing market demand for the construction materials needed. Traditional methods of production, which do not take into account of the chemical and mineralogical characteristics, are practiced. Few studies have been made of the clays used in the brickworks or of raw materials used for pottery in Uganda. (Harris, 1946) and (Kagobya, 1950) studied the clay deposit at Ntawo, 25 km from Kampala on the Jinja road. It was reported that Ntawo clay exhibited marked shrinkage and cracked on firing, and the quality of product was inferior when it was evaluated for pottery production. (McGill, 1965) studied the nature and distribution of clays from several occurrences around Kampala, and determined their plasticity with a view to establish a fine ceramics industry. (Tuhumwire et al., 1995) measured the physical properties and discussed the geology of the Kajjansi and Kitiko deposits located 13 km from Kampala on the Kampala– Entebbe road. A study of some clay samples from various deposits in Uganda indicated that they are mediumquality kaolinitic–illitic clays (Nyakairu & Kaahwa, 1998) There is ample demand for quality bricks and other clay products, and thus, this study investigated the mineralogical and chemical characteristics of the raw material used and the durability of locally-produced burnt clay bricks and development of a quality control management plan for the local manufacturing industry. This will help to give a better understanding of the clay materials, as well as of their geochemistry. Properties of laboratory-produced burnt bricks from Mukono and Wakiso clays were compared with burnt bricks available on the market but produced from the same clay sources. Burnt bricks produced in the laboratory were fired at 650oC, 750oC and 1100oC to investigate the effect of firing temperature on brick properties. The results show that burnt bricks fired at high temperatures are more durable and have better chances of survival in aggressive environments than bricks fired at low temperatures. The differences in durability in the environments studied are due to variation in the chemical composition of the clays which resulted in different properties of burnt bricks. Careful control of clay composition and firing temperature can produce durable burnt clay bricks with high durability, that remain unaltered in the process of their service life even in aggressive environments.