EFFECT OF CINDER ASH AS AUXILIARY ADDITIVE MINERAL IN HYDRATED LIME TREATMENT FOR EXPANSIVE SUBGRADE SOIL FOR ROAD CONSTRUCTION (CASE STUDY, WOLAITA SODDO TO OMO RIVER ROAD PROJECT, ETHIOPIA)

Abstract

A road is one of the most critical infrastructures for the community's development, because it is one of the most ground routes for any other socio-economic interaction. Based on road life and its economic considerations, road pavement designs mainly need good sub-grade soil. The soil in the Wolaita area were lateritic clay. However, the road construction site soil does not fulfill the sub-grade soil requirements. Hence hundreds of millions of metric cube soil are needed for the sub-grade layer, and the same volume of soil is cut to drop site in one road project. Therefore, thisresearch work comes up with the conjugation of random distributed local natural cinder ash with hydrated lime to improve the problematic sub grade soil. In general, the research work comprises the tasks such as characterization and selection of representative problematic soils and cinder ash and hydrated lime mixtures. Method of characterization is done as per AASHTO and ASTM test methods which are recommended in Ethiopian Road Authority (ERA). Cinder ash by weight on the soil's improvement; CBR, surcharged swell, dry density, moisture content, and their optimum improvements were discussed. The percentage of cinder ash and hydrated lime in the soil were, 20%, 25%, 30%, 35% and 2%, 3%, 4%, and 5%, respectively. The result showed that MDD is increased and OMS is decreased with increased cinder ash and lime percent. The three-point soaked Cbr test indicated that, the value increased from 2.7% to 12.8%, this result shows that, the CBR value is increased by 374.074% from the native soil CBR value when the expansive soil is treated with the mixture of 35% of cinder ash and 5% of