Determination of Effective Wood Ash Proportion for Black Cotton Soil Improvement

Expansive soils are usually treated by different soil stabilization methods in order to use as the subgrade. Soils mix with stabilizers in proportion. This research aims to determine the effective wood ash proportion to stabilize black cotton soil. The laboratory work is conducted to determine the various geotechnical properties of the soil sample. The preliminary investigation of the soil sample shows that it belongs to A-7-5 class of soil, according to the AASHTO soil classification system. Wood ash is added in the stepped mass percentage of 5%, 10%, 15%, and 20% by dry weight of the soil. Stabilized soil samples are also cured for 7 days for Atterberg limit, compaction and soaked for four days for California Bearing Ratio tests. Experimental analysis shows that wood ash reduces plasticity index, swelling, and optimum moisture content. Conversely, wood ash can increase California Bearing Ratio, maximum dry density, and unified compressive strength with an increment of wood ash. The effective wood ash proportion for black cotton soil stabilization is 10%-15% of the soil mass with the tendency to get a better result between 13%-15%.