Abstract:
The transport infrastructure is facing a number of difficulties including a growing problem with
road pavement deterioration. Some of the cause of this deterioration is the presence of expansive
soil in the subgrade. This type of soil is characterized by low shear strength, high
compressibility, and plasticity. To improve the properties of this soil; one of the commonly used
method is stabilization. The preliminary investigation of the collected soil samples from eight
pits of the Achamo-Bonosha road stretch shows that they belong to A-7-5 class of soil in the
AASHTO soil classification system, CH and MH under unified soil classification system. Soils
under this class are generally does not meet the subgrade soil specifications. This study aimed to
investigate the suitability of treated expansive soil with lime and cement to be used as a sub grade road. The experimental works were carried out for natural soil alone, soil-lime, and soil cement mixes. A series of laboratory tests including as moisture content, specific gravity,
Atterberg limits, particle size distribution, free swell, compaction, and California bearing ratio
tests were conducted. 3%,6%,9%, and 12% contents of lime and cement were used independently
by mass of dry soil for each tests. LL, PI, OMC, and CBR swell were decreased with increasing
cement and lime contents from 3% to 12%. While PL, MDD and CBR were increased as cement
and lime contents were increased. The optimum percent usage for lime treated soil was obtained
at 9%, but for cement treated soil the optimum percent usage was obtained at 6%. The curing
periods like 7 days,14 days and 21 days have been made a significant role in changing the
plasticity properties of expansive subgrade soil treated with lime and cement. Lime was needed
longer curing period and its 9 % content while cement was needed shorter periods and its 6%
content to fulfil the specification criteria of improved expansive subgrade soil. In general, it is
concluded that treating soil using 6% cement content and 9% lime content is an effective and
optimum improvement solution for expansive subgrade soil which meets the sub-grade
requirements and specifications.
