Comparative Study on The Improvement in Engineering Properties of Expansive Soil Modified with Stone Dust and Brick Dust for Sub Grade Case in Jimma

Abstract

Expansive soils are difficult to use as construction material for highways, airfields and lightweight structures. Expansive soils are susceptible to considerable volume changes due to seasonal variations and moisture content; light weight structures cannot exert the necessary counter load to overcome the swelling from expansive soil. The availability of expansive soil along the alignment of road projects has a significant influence on planning, design, construction, and maintenance of the road. Therefore, the aim of this study is to evaluate and compare the improvement in engineering properties of expansive soil modified with stone dust and brick dust as a sub-grade soil. Several methods have been developed for successful improvement of expansive Soils. For this study two sub grade soils were collected from Jimma Town around Shanen Gibe (jimma bus station) and around Merkato. A Soil samples were collected from depth of below 1.5m. Laboratory tests were conducted to determine moisture content, free swell test, grain size analysis, specific gravity, Hydrometer test, Atterberg limits, compaction test, California Bearing Ratio and CBR swell tests. Depending on the tests conducted in the laboratory the optimum percentage of stone dust and brick dust obtained were at 20% and 40% respectively. The laboratory test result confirmed that, modification of expansive soil with stone dust and brick dust improves its engineering properties of expansive soil. From the analysis results, the CBR value is increases from the 1.78% to 21.7% by using stone dust and from 1.78% to 8.75% by using brick dust at the optimum percentage. Addition of both stone dust and brick dust increases the plastic limit and decreases the liquid limit and plasticity index of the expansive soil sample. Generally, as the addition of both stone dust and brick dust ratio increased the FS, LL, PL, OMC, CBR swell decreased and inversely the PL, MDD are increased and recommended that modification of expansive soil with stone dust can be used to increase the strength capacity of foundation and subgrade. In addition both the stone dust and brick dust can be gained with low cost, locally available and finally makes the environment to become safe.