IJSTE - International Journal of Science Technology & Engineering | Volume 2 | Issue 12 | June 2016 ISSN (online): 2349-784X All rights reserved by www.ijste.org 435 Impact of Micro Silica Fume on Engineering Properties of Expansive Soil Shivangi Bharadwaj Dr. M. K. Trivedi PG Student Professor Department of Civil Engineering Department of Civil Engineering Madhav Institute of Technology and Science Madhav Institute of Technology and Science Abstract Black cotton soil deposits in India are a boon to farmers but are problematic to civil engineers. Civil engineering structures experience large scale damage due to heaving accompanied by loss of strength of these soils during rainy seasons and shrinkage during summer. Buildings crack, canal linings slide, beds of canals heave, roads get rutted and retaining structures etc. Stabilization of such soils has been traditionally relied on treatment with lime, cement and waste materials such as fly ash. Micro silica is waste material obtained from electric arc furnaces. This paper presents an experimental investigation, carried out to study the effects of Micro Silica Fume on index properties of black cotton soil. A series of laboratory experiments have been conducted on samples with 0%, 5%, 10% and 15% of Silica Fume by weight of dry soil. The test results showed a significant change in consistency limits of samples containing Silica fume. The Liquid limit would increase by 50% to 67% and Plasticity Index would increase from 24% to 31%. The shrinkage limit would increase from 10.44% to 13.01% and specific gravity would decreased by 2.69% to 2.59%. Also the Differential Free Swell decreased from 48.46% to 9% showing appreciable decrease in swelling behaviour. The investigation showed that the Silica fume is a valuable material to modify the index properties of black cotton soil to make it suitable for different construction activities. Keywords: Black Cotton Soil, Free Swell Index, Index Properties, Micro-Silica Fume, Standard Proctor Test ________________________________________________________________________________________________________ I. INTRODUCTION The design foundation on black cotton soil (expansive soil) has always been a difficult task for the engineers as the structure resting on black cotton soil cracks without any warning. Black cotton soil is found in M.P., Karnataka, Maharashtra and Andhra Pradesh in our country. Soil proportion changes depending upon their constituents, i.e. water content, density, bulk density, angle of friction, shear strength etc. In terms of geotechnical Engineering, Black Cotton soil is one which when associated with an engineering structure and in presence of water will show a tendency to swell or shrink causing the structure to experience moments which are largely unrelated to the direct effect of loading by the structure. The properties of black cotton soil can be modified by stabilizing the soil with the use of additives or by mechanical means. Soil stabilization techniques are used to improve shear strength, CBR, reducing expansive characteristics, etc. Silica fume also referred as micro-silica is a product resulting reduction of high purity quartz with coal in an electric arc furnace in the manufacture of silicon or Ferro-silicon alloy. Silica fume rises as an oxidized vapour. It cools, condenses and is collected. It is fine grey coloured powder sometime similar to Portland cement or some flashes. Condensed silica fume is essentially silicon-dioxide (more than 90%) in non-crystalline form. Since it is an air borne material line fly ash it has spherical shape. It is extremely fine with a particle size less than 0.1 micron and specific surface area of about 20,000m²/kg. Silica fume is used as an artificial pozzolanic admixture in concrete. As far as the production of silica fume is concerned nearly 100,000 tons of micro silica is produced each year world wide².Iron also has a large amount of micro silica production. Steel Authority of India has provided necessary facilities to produce more than 3000 tons of Silica fume annually³. Many waste materials are used to modify the characteristics of soft soils. Traditionally the soils are stabilized by lime, cement, etc. In recent year the uses of waste materials like fly ash,plastic, rice- husk ash, slag,etc for soil stabilization is gaining importance. In this study attempts are made to find the effect of silica fume on engineering characteristics of black cotton soil. II. LITERATURE REVIEW The engineering properties of clayey subgrade soils may need to be improved to make them suitable for construction using some sort of stabilization methods. Stabilization of pavement subgrade soils has traditionally relied on treatment with lime, cement, or waste materials such as fly ash, slag, Silica Fume etc. Many researchers are looking for alternative materials for soil stabilization, fly ash is an effective agent for chemical and mechanical stabilization of soil.[1-2] Biswas et al.(2012) studied the utilization of rice husk with lime in subgrade soil for a rural road; they concluded that a very little amount of lime (3%) added to the clayey soil with RHA, improve the CBR value and compaction characteristics to a great extent.[3]