Abstract:
Common problem with a series of challenges in Ethiopia is road pavement failure. The most
likely cause of this failure is presence of expansive soil in the subgrade. The main objective of
this thesis presents a study on identification of natural subgrade and improving compaction
and CBR properties of expansive soil of Daye-Girja Road by using pumice in varying
quantities. The experimental investigation was carried out for natural soil alone, and soilpumice
mixes. A series of laboratory tests, such as moisture content, specific gravity, Atterberg
limits, particle size distribution, free swell, compaction, and CBR tests, were conducted before
and after adding pumice in (5%, 10%, and 15%) percentage by weight of expansive soil. The
MDD values were increased, and OMC decreased with the addition of pumice. The optimum
pumice content to stabilize expansive soil were taken as 15%. The plasticity index of the soilpumice
treated sample after the curing periods of the first 21days 9.12%, 7.14%, and 5.43%,
were obtained and California bearing ratio of 11.2%, 10.8% and 10.6% respectively obtained
at 14 day curing period. And also, the results show that pumice provides better property
improvement in term of liquid limit, plastic limit, plasticity index, compaction and California
Bearing Ratio values are increased as pumice content increased with increasing pumice
content. In general, stabilizing soil using 15% pumice content improves expansive subgrade
soil, fulfilling sub-grade requirements and specifications of ERA manual and it is a costeffective
than excavating and filling selected material
