Development of raw soil building bricks as an alternative to fired clay bricks
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Uganda has a fast-growing population. The current population of Uganda is 48,100,403 based on projections of the latest United Nations data. The population growth rate is currently at 3.32%, and has remained around 3% for the past several decades in Uganda. The overall distribution of households by construction material of the wall revealed that 69 percent of the households in Uganda lived in dwellings that had brick walls while 28 percent of households had dwellings with walls made of mud and poles. The clay brick is traditionally manufactured by mixing the ground clay with water then forming into desired shape and size, drying and firing. This method of making bricks is called firing clay bricks. In this method, firewood is the fuel used. Usually, one ton or 3𝑚3 of firewood is needed for every 1,000 bricks. Providing the firewood requires cutting down trees. This has increased the rate of deforestation in Uganda. This, in turn, has degraded the environment. This study was focused on developing raw soil building bricks as an alternative to fired clay bricks. Samples of bricks were made and their quality was tested in terms of compressive strength and water absorption. Some of the samples were made using raw soil, cement, calcium chloride and kaolin, while others were made using raw soil and cement only. The cement percentage composition was varied from 5% to 8% among the samples made. The bricks were then left to sun dry for 21 days and then tested for compressive strength and water absorption. Fired clay bricks were also bought and tested for compressive strength and water absorption. The compressive strength test was carried out using Universal testing machine. The highest average compressive strength of the raw soil bricks was 2.428 N/mm2 for the bricks that contained soil, cement, calcium chloride and kaolin, while the highest average for the bricks which did not contain calcium chloride and kaolin was 2.236 N/mm2. It was observed that bricks that had additives had higher compressive strength than those that were made without the additives. This is because additives improve the compressive strength of bricks. The raw soil bricks that had composed of 8% cement had higher average compressive strength than those with lower cement composition. However, fired clay bricks had a higher average compressive strength than the raw soil bricks by 1.092 N/mm2.The compressive strength of the fired clay bricks was averagely 3.52N/mm2. The percentage of water absorption of the fired clay bricks was 2.7% and it was lower than that of the raw soil building bricks. Percentage of water absorption of raw soil building bricks decreased with increase in the cement composition. The bricks with 8% cement composition had water absorption percentage of 4.73% which was lower than that of the bricks with percent cement composition of 5%. The raw soil building bricks made without additives (kaolin and calcium chloride) are cheaper than those made with additives and also cheaper than the fired clay bricks.