Effect of compaction conditions and state variables on engineering properties of the lime stabilized soil

Abstract

To observe the effect of state variables on the strength of the lime stabilized soil, test samples were prepared by varying lime content, moisture content, compactive effort, compaction delay time, mixing method and soil type. Three types of soil collected from three different areas of Bangladesh were selected for the research work. Two types of soil was CL and other type was ML, according to the Unified Soil Classification System. According to AASHTO Soil Classification System the three types of soils are A-6, A-7-6 and A-4 type. Slaked lime was used for stabilization. Unconfined compressive strength test and by CBR test was performed on the stabilized soil. Strength increase of the lime stabilized soil is highly dependent upon the soil type. In general, fine grain soils are suitable for lime stabilization. Addition of 3% lime produces significant increase in strength of the stabilized soil. Due to the increase oflime content from 3% to 5%, the increase in strength is not significant. The maximum dry density of the soil is reduced due to the addition oflime. The maximum dry density decreases with the increase of lime content. Optimum moisture content of the stabilized soil increases due to the addition of lime and the optimum moisture content continues to increase with the increase of lime percent. The maximum strength of the stabilized soil occurs at a moisture content higher than the optimum moisture content of the soil at which maximum dry density is achieved. When wet soil is difficult to compact, lime stabilization may be helpful. The strength of the stabilized soil increases rapidly with the increase of compaction energy upto a certain level. After that the rate of increases of strength is gradual. The increase of strength is rapid upto about half of the Standard Proctor energy. There is practically no change in strength due to delay in compaction of 6 hours after mixing. About 5% decrease in strength Occurs due to the compaction delay time of 24 hours and about 12% decrease in strength Occurs due to the compaction delay time of 48 hours. Unconfined compressive strength of the lime stabilized soil increases with the increase of age of the stabilized soil. For clay soils, seven days strength is about 70% of28 days strength.