COMPARATIVE STUDY ON THE EFFECT OF THE CEMENT AND LIME ENHANCEMENT ON EXPANSIVE SOIL OF ACHAMO-BONOSHA ROAD PROJECT, HADIYA ZONE, ETHIOPIA

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.