Stabilization of expansive soil using combination of Sawdust Ash and Lime.

Abstract

This study was conducted to examine the effects of the Sawdust Ash (SDA) and Lime on Atterberg’s limits, compaction characteristics, California bearing ratio, and unconfined compressive strength of expansive soil collected from Jimma Town, Oromia, South-western Ethiopia. The sawdust waste collected from the local factory and burnt to gets ash whereas lime was purchased from local market. The expansive soil – sawdust ash – lime mixed proportions were prepared by 95.5% -3%- 1.5%, 92.5%-5% - 2.5%, 85% -10%- 5%, and 78.5%- 15%-7.5% to evaluate the effects of SDA and lime. The grain size analysis and Atterberg’s limit tests were conducted to classify the soil collected from the study area. The results obtained from wet sieve analysis and hydrometer test were plotted on semi-log scale versus arithmetic scale. The results showed that, the percentage of soil passing sieve no.200 (0.075mm) varied from 87.45% - 94.7 % for different soil samples and Atterberg limits test results showed that, the liquid limit varied from 80 to 97 %, whereas the plasticity index varied from 50 to 65 % for air-dried specimens. This indicates that soil under the study area is CH according to unified soil classification systems and A-7-5 based on the AASHTO classification systems. The effect of SDA and lime on the properties of expansive soil indicates the liquid limit decreases, plastic limit slightly increases which causes reduction in the plasticity index. The maximum dry density of expansive soil increases as small contents of SDA and lime added. However, this value decreases as amount of SDA and lime increases. The optimum moisture content increase as the content of SDA and lime increases. The CBR values of soaked samples increased with the addition of SDA and lime and the peak values were achieved at 5% SDA and 2.5% lime contents. The study shows that treating of expansive soil with SDA and lime changes the behavior of natural soils from very poor subgrade to fair subgrade.