Abstract:
In road construction, expansive soils are the most common problem encountered in the world, as
well as in Ethiopia. To overcome these problems, the expansive soil needs to be stabilized by using
different techniques and materials or removed and replaced by better materials for subgrade
formation. Cement and lime are common materials used for the stabilization of weak soil for
subgrade formation. Nowadays, in addition to common stabilizing materials, locally available
materials are also used for soil stabilization. Barley is highly produced in Ethiopia, especially in
the Oromia region in the Arsi and Bale zones. The beverage industries are growing fast and
consume barley for the production of different alcohol and non-alcohol drinks. Hence barley husk
ash from Assela Malt Factory was studied and used for the stabilization of expansive soils for
subgrade soil formation with lime. The sampling and test methods used in this research are
according to ASTM and AASHTO test methods. The results were analyzed according to the
guidelines of the ERA pavement design manual. In this study, the expansive soil was sampled
from three different locations of Jimma Town and tested with 0%, 10%, 15%, and 20% of lime to
obtain an optimum percentage of lime. The optimum amount of lime used was 10% and the PI,
LL, PL, SG, OMC, MDD, CBR, Free swell and UCS values obtained at optimum lime content are;
22%, 52%, 30%, 2.59, 22.8%, 1.423g/cm3, 9.72%, 42%, and 137kpa respectively. The
microstructure of the soil treated with 10% lime had less void showing denser compared to
untreated soil. A varying amount of BHA was added to check its effect on the results obtained
using optimum lime content. The optimum amount of BHA used with lime is also obtained at 10%.
Hence lime and BHA used for this study percentage by weight are 10% lime and 10% BHA. Test
result values obtained at 10% lime and 10% BHA for PI, LL, PL, SG, OMC, MDD, CBR, Free
swell, and UCS values are; 18%, 49%, 31%, 2.25, 27.2%, 1.315g/cm3, 18.42%, 33%, and 101kpa
respectively. The microstructure of the soil shows that the particles are closely spaced which is the
indication for the tendency of blended materials to form a better material. BHA improved most of
the engineering properties of the soil and satisfies ERA pavement design manual requirement
hence, it can be used as a partial replacement with lime for subgrade soil stabilization.
