Proceedings of the International Conference on Mechanical Engineering and Renewable Energy 2013 (ICMERE2013) 1-3 May 2014, Chittagong, Bangladesh ICMERE2013-PI-229 © ICMERE2013 1. INTRODUCTION Lime is widely used due to low cost, availability and its efficiency. Change in clay soil moisture is often accompanied by volume change. Swelling is usually observed in unsaturated clays with specific mineralogy. These soils have high water absorption capacity so they Absorb the water and their volume increases. Soil contraction and swelling depends on various factors including: - The type and amount of clay minerals in soil constituents - Soil moisture - Soil dry density Important impact of lime on Soil is increased workability, decreased swelling and soil contraction as well as increased soil resistance Including compressive and tensile strengths. Ion exchange reactions between clay and lime particles Overall adding lime to the soil leads to developing interactions in the soil which practically causes improvement of soil quality and characteristics in terms of geotechnical engineering aspects. Lime stabilization may lead to _ reduced plasticity index _ increased efficiency _ improved strength properties of soil _ decreased swelling One of the effects of lime on clay is changing Atterberg limits so that adding lime causes decreased Plasticity index of the soil. When lime is used with a clay soil some chemical reactions occurs. Such as 1. ion exchange reaction 2. lime carbonation reactions 3. Pozzolanic reactions 1. Ion Exchange Reaction [5] Calcium ions Ca++ in lime do ion exchange with soil cations and low-capacity ions are replaced by calcium ions in soil. It causes concentration of calcium ions around clay particles thus electronic density changes around clay particles and soil plasticity decreases and soil operation in various projects of foundation, infrastructure and road construction is improved (Al-Rawas, 2002). 2. Lime Carbonation Reactions [5] Formation of CaCo3 and MgCo3 is result of reaction between lime and carbon dioxide in air. Calcium carbonate and magnesium materials are poorly adherent thus it necessary to prevent from excessive progress of this interaction (Abdullah, 1999). 3. Pozzolanic Reactions The reaction between water and soil with lime and silica and alumina materials of the soil leads to development of cementing material in the soul which and it is done increases soil resistance and stability. This reaction is a [5] Abstract-Swelling soils account for large volume of the ground. These soils are Swelled due to moisture changes in different seasons of the year which leads to damage and Crack to structures built on these soils and considerable financial loss would be incurred. Thus this phenomenon may be described as dangerous like other natural disasters. Soil Stabilization is a good technique for reducing such loss. Mechanical techniques such as Concentration leads to improved soil characteristics. However, authors have concluded that chemical stabilization of the soil is more effective. In this paper, lime is used as a Stabilizing chemical for swelling soils. Soil samples with plasticity index 31.1were used in experiment. Plasticity characteristics of clay soils in the region regarding mentioned samples are studied and compared using combination of various percentages such as 2%, 4%, 6% and 8% of lime. From the observation author find 4%lime as modifying agent to optimize plasticity index value. Keywords: Liquid limit, Plastic limit, Plasticity index, Pozzolanic, Stabilization. IMPROVEMENT OF PLASTICITY INDEX VALUE OF SEWLLING CLAY SOIL BY LIME STABILIZATION Mohammad Imran Hossain 1 , Asaduzzaman Khan 2 , Md. Hafizul Haque 3 and Sultan Mohammad Ferooq 4 1 Department of Civil Engineering, National Poly-technique Institute, Dhaka, Bangladesh 2 Project Engineer, Project Operation, Trust Alliance Technology Ltd, Dhaka, Bangladesh. 3 Department of Civil Engineering, America Bangladesh University, Dhaka , Bangladesh. 4 Department of Civil Engineering, CUET, Chittagong, Bangladesh. 1 imrancuet07@yahoo.com, 2,* asad.cuet@yahoo.com, 3 hafizcuet07@yahoo.com, 4 faruquesm1@yahoo.com