INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 02, FEBRUARY 2020 ISSN 2277-8616 5714 IJSTR©2020 www.ijstr.org Stabilization On Expansive Soil For Civil Engineering Projects Dr. Subash Thanappan 1 , Michael Tesfaye 2 , Siyane Tariku 3 , Tajudin Abdulahi 4 , Shibelay Abebe 5 Abstract: The selection of the suitable soil type for construction is a challenging job for civil engineers as the expansive soils are not suitable for the construction of houses, commercial buildings and mainly for highway projects as its engineering behaviors in reaction with water may considerably reduce the strength and thus damages to the civil engineering structures. Keeping this under consideration, the soil samples were excavated from five different locations and taken for their geological assessment by performing the various physical tests such as Specific gravity test; Sieve analysis, Hydrometer analysis; free swell index test; Atterberg limits and Compaction test for the unstabilized expansive soil samples in IOT Laboratory, Ambo University, Ambo, Ethiopia. In the current study, the additives and techniques have been applied using the lime as a special ingredient for stabilizing the expansive soil, particularly, which has been focused with respect to improving the efficiency of their physical properties. Eventually, it was concluded that the application of lime helps for improving the physical properties of the expansive soil. Index Terms: Black Cotton Soil, Expansive soil, Free Swell Index, Lime, Plasticity Index, Textural Class, Weaker Cations —————————— ◆ —————————— 1. INTRODUCTION As the Soil is the essential sediments or other accumulation of minerals, and it’s a valuable component in an ecosystem, the addition of some binders with soil enhances a moral support so that soil particles get in contact to raise the water holding capacity and to build the pressure resistant and thus improving its physical and chemical characteristics [5, 6]. About 5% of the global area occupies with Black Cotton Soil (BCS) and mainly found in Sudan, South Africa, Ethiopia and Tanzania. The low shrinkage limit and high optimum moisture content and highly sensitive to moisture changes are the nature of BCS and hence its undesirable factors to be modified using some suitable stabilization mechanisms [4], [9]. Pavements are in particular susceptible to damage by expansive soils because they are light weight and extended over large areas [10]. The reduction in the strength and damage of the structure is mainly due to the changes in the physical properties and behavior of soil is due to the reaction with water. Stabilization of soil involves the methods used for modifying the property of a soil to develop its engineering performance [4]. Its value helps to some extent in identifying and classifying soils. A better idea about suitability of the soil as a construction material; the higher value of specific gravity gives more strength for highways work and foundations. Soil stabilization is a technique that uses other materials to improve the durability of soil by increasing its strength and resistance to water [7], [8]. Though there are several methods that have been used to recognize the presence of expansive soils a need of fast and relatively cheaper methods continues to be a necessary under taking. The most commonly used stabilizer for the expansive soils are; bitumen; lime, and cement. According to the Pioneer Researchers, the stabilization of this soil with bitumen: lime or cement is effective [2], [3]. Regrettably, the costs of these stabilizers are high making them economically unattractive. Recent trend in research works in the field of geotechnical engineering and construction materials focuses for the cheap materials and the locally easily available ingredients as the best stabilizing agents [5],[9]. 2 MATERIALS AND METHODS The soil samples from five different locations were collected during the period March – April 2018 with shovels at depths varying from three to four meters below the grade. The samples were jam-packed in five different bags, carefully tagged for identification purpose and transported to Materials Testing Laboratory, Civil Engineering Department, Institute of Technology, Awaro campus, Ambo University, Ambo, Oromia region, Ethiopia. The soil samples collected were kept for air – drying using the number of trays (labeled with the location names) at the civil engineering laboratory. All the soil samples were tested (Figure-1) for the identification of the type of soil by doing the Sieve analysis and Hydrometer analysis, determination of specific gravity (G), Free Swell Index (FSI), and Plasticity Index (PI) using the standard procedures, and the maximum dry density as well as the maximum water content by performing the compaction test. The stabilization of the expansive soil was done using the lime as a special ingredient and the results were compared with the natural soil. 3 RESULTS AND DISCUSSION The sample result for sieve analysis on sample-1 is shown in Table-1. The test results on sieve analysis for the other samples will be discussed. The particle size curve produced under the hydrometer (sedimentation analysis) for soil sample -5 shows 60% of soil grains passing through 0.02 mm which is indication that clay percentage is dominating more in the soil sample. The gradation (mechanical composition) of each sample is presented in Table-2 where the sample-5 collected from Awaro campus was taken for the hydrometer analysis and found to be 60% of clay and the silt amount is of only 8.4% as shown in Table-3. The plasticity index of soil samples shown in Table-4 varies between 26.25 and 55.40. Soil PI closer to 17 indicate that the soil is medium to Expansive potential; PI closer to 25 is High expansive, PI closer to 30 is highly expansive and PI close to 40 is Very high expansive ___________________ • Subash Thanappan is the faculty member in the Department of Civil Engineering, IOT, Ambo University, Ethiopia, PH-00251939722372. E-mail: thanappansubash@gmail.com • The Co-authors - Michael Tesfaye, Siyane Tarik, Tajudin Abdulahi , and Shibelay Abebe are the graduated students from the Department of Civil Engineering, IOT, Ambo University, Ambo, Ethiopia E-mail: mickytesfaye21@gmail.com 2 , siyanetariku678@gmail.com 3 , tajuabdulahi@gmail.com 4 , shibelayabebe@yahoo.com 5