EXPERIMENTAL STUDY ON STABILIZATION OF BLACK COTTON SOIL BY BREWER SPENT GRAIN ASH FOR ROAD SUBGRADE CONSTRUCTION

Expansive soils form a major soil group in Addis Ababa and occur in mostly Bole, Nifas silk lafto, Akaki Kality and in some extent available other parts of the sub city and in most cases the major clay mineral component is montmorillonite. For the past twenty years, those lands have been used for agriculture and Addis Ababa is widened by road and buildings, the problem of the land become more prominent in those sub cities because of that, various studies and road improvements were needed. The performance of roads depends upon the quality of subgrades. A stable subgrade helps to produce a long-lasting pavement due to support provided to the pavement system, therefore the quality of the subgrade will greatly influence the pavement design and the service life of the pavement.
This research work is aimed to investigate the performance of brewer spent grain ash for stabilization of expansive clay soil. The laboratory work involved index properties to classify the soil sample. The preliminary investigation of the soil shows that it belongs to A-7-5(20) class of soil in the AASHTO soil classification system. Soils under this class are generally of poor engineering use. Atterberg limits, free swell, specific gravity, modified compaction, unconfined compressive strength and 3Point-CBR tests were used to evaluate properties of stabilized soil. The soil was stabilized with brewer spent grain ash in stepped concentration of 10%, 20% and 30% by dry weight of the soil.