Engineering Properties of Expansive Clay Stabilized with Cement and Lime for Subgrade in Road Construction: A Case Study of Jimma Town.

Abstract

Expansive soils are characterized by volume change in that these soils swell when wet and shrink when dry. Since moisture change in soils bring change in volume mass of the soils it brings severe movement of structures built on such soils experiences cracking and progressive damages. Therefore, these problematic soils when encountered as sub grade should be avoided or treated properly. The objective of this study was to quantify the improvements achieved on the engineering properties of expansive soils due to cement and lime stabilization. Soil stabilization is a process whereby increased strength and stability of the soil is attained mainly by mechanical or chemical means. Today stabilizing soils with Lime and Cement is a cost effective method of converting poor quality soil into a strong impermeable medium. For this study two sub grade soils were collected from Jimma Town around Shanen Gibe Hospital along Seka road and around Kidenameret Church. Laboratory tests were conducted to determine moisture content, specific gravity, grain size analysis, Atterberg limits, proctor test, free swell test, California Bearing Ratio and CBR swell tests. The test procedures were based on AASHTO and ASTM laboratory test standards. The test results show that the sub grade soils are A-7-5 as per AASHTO soil classification system and CH as per USCS. As far as the engineering properties of natural sub grade soils were studied the two soils were Expansive clay soils. The two soils have almost similar engineering properties but, they were different in color. The sample from around Shanen Gibe Hospital was light gray clay and the one from around Kidanemeret Church was dark gray clay. The collected samples of the soils were stabilized using 2, 4, 5, 6, 7 and 8% of hydrated lime and 10, 12, 14 and 16% of cement by weight. The optimum ratio for the studied expansive soils were 5% using hydrated lime and 14% using cement. The improvement of sub grade soil properties were increased with increased ratios of hydrated lime and cement. The maximum improvements on engineering properties were observed on CBR and minimum improvements were on liquid limits. The result indicated that the two stabilizers were very effective in improving strength parameters than index parameters. It was observed that cement was better than hydrated lime in improving sub grade soil properties. But using cement is not economical due to its highest optimum ratio and current market cost compared to cost of hydrated lime. The results of this study show that the cement and hydrated lime stabilized soils under optimum ratio full fill the standard requirements as sub grade soils. For the practical applicability of the stabilized soils further detail investigations including chemical and mineralogical analysis of the treated soils will of paramount.