1. The document presents the results of an experimental study to stabilize expansive soils from Jimma, Ethiopia using mixtures of pumice and lime for subgrade road construction.
2. Laboratory tests found that the pumice contained high levels of silicon dioxide and aluminum oxide meeting standards for pozzolanic materials. Mixing lime and pumice reduced the plasticity index and increased the strength of expansive soils as measured by their California Bearing Ratio.
3. The optimum mix ratio found was 7% lime and 3% pumice, which decreased plasticity and increased the maximum dry density and bearing capacity of the soils making them suitable for use as subgrade material.