Comparative Study On The Engineering Property Of Groundnut Shell Ash, Coal Ash And Bamboo Fiber Stabilized Expansive Subgrade Soil: A Case Of Gambella Town

Abstract

Construction and subsequent maintenance of pavements in good condition has become quite problematic especially in areas where soft or expansive soils are available along the selected route. To solve this problem, soil improvement is necessary because it not only lowers the construction cost (compares with lime, cement etc) but also minimize the risk of any damage of structure later on. The role of groundnut shell ash, coal ash and bamboo fiber in improving the characteristics of expansive sub grade material is analyzed. Generally stabilization of expansive soil using industrial and agricultural wastes is economical and safe for environment. To realize the desired objective a purposive sampling techniques which is non-probability method was adopted. Two expansive subgrade soils were taken for the study by observation and free swell index tests at depth of 1.5m to remove organic matters. The general objective of this research is to compare the engineering properties of groundnut shell ash, coal ash and bamboo fiber stabilized expansive subgrade soil. The preliminary investigation of the soil shows that it belongs to A-7-5 class of soil in AASHTO and CH in USCS. The BD soil sample has plastic index 49.44 %, free swell index 80 %, linear shrinkage 12.33% and CBR value 2.2%. In addition, the MS soil sample has plastic index 55.86%, free swell index 85%, linear shrinkage 14.02% and CBR value 1.6%. Since both the given soil sample before any stabilizers are added was very high expansive according to their plasticity index and CBR value as comparing with standards and specifications. The soil sample stabilized with different percentages of coal ash ranging from 0%-50% at an interval of 10%, bamboo fiber (1%,1.5%,2%,2.5%, 3%) and groundnut shell ash(2%, 4%, 6%, 8% & 10%). The analysis of the result shows that (8% GSA, 40% CA and 2.5% BF) was an optimum ratio which achieved by most geotechnical parameters of the study. Comparatively it is observed that Coal ash is effectively improving the engineering property of expansive subgrade soil better than groundnut shell ash and bamboo fiber. The addition of those additives reduces LL, PI, CBR Swell and the optimum moisture content with an increase in PL, MDD & CBR with an increase of additives. A considerable amount of cost savings is also possible when the expansive subgrade soil is stabilized with GSA, CA and BF compares with common stabilizer (lime and cement). Additional parameter like PH value test, volumetric shrinkage and mineralogical tests should also be performed to have more realistic test results.