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
