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Browsing Dissertations by Author "Aaron Rachkara"
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Item Assessing the Use of Sewage Sludge Cake Ash in the Stabilization of Black Cottton Soils(Uganda Christian University, 2025-04-14) Aaron RachkaraThis research addresses the improvement of the engineering properties of black cotton soils treated with sewage sludge cake ash for use in the subgrade layer. The property of black cotton soils that this research banks on are heavily influenced by the high amount of montmorillonite clay mineral of upto about 70% to 80%. These soils fall under the order Vertic Cambisols usually formed from the weathering of basaltic rocks. It is noted that they are defined by a very low California Bearing Ration (CBR), high plasticity index and do not do well when subjected to loading in the unconfined compressive strength test (UCS). In addition to these physical properties, the chemical aspects also play a huge role since these soils have a high affinity for water. It is on these factors that the use of sewage sludge cake ash was proposed since the ash has a lot of pozzolanic compounds that when treated with the montmorillonite will produce a cementitious compound. The soil sample was picked from Kitgum Orom road. These tests were the Atterberg limits, particle size distribution, California bearing ratio, Unconfined compressive strength after treatment and the sewage sludge cake ash was subjected to an X-ray diffraction test. The tests confirmed it was indeed black cotton soil and that the ash had the necessary compounds to act as a pozzolan. The soil was treated with the black cotton soils at 5%, 10%, 15% and 20%, the optimum was found to be at 15% giving a CBR of 15.3%, plasticity index of 14.8% and a UCS of 0.33MPa. This deduced that the SSCA could improve the soil to the level of a G15 subgrade material with addition of some bio additives to improve its load bearing capacity.