Micro-structural and Mineralogical Studies to Evaluate the Effectiveness of Industrial Solid Wastes for Stabilization of Expansive Soils

Abstract

AbstractExpansive black cotton soils undergo large volume changes due to swell and shrinkage due to seasonal moisture fluctuations during wet and dry seasons causing severe problems to lightly loaded structures, such as buildings, pavements and pipelines founded on them. Before undertaking any construction activity, the foundation soil should be properly stabilized. The best way to overcome the problems associated with the expansive soil is by stabilization with pozzolanic materials such as hydrated lime and Portland cement stabilization. However, as they may not be economical as well as to reduce the problem of disposal, many industrial and agro-industrial wastes such as rice husk ash (RHA), and bagasse ash (BA) and carbide lime (CL) which resemble the properties of lime and cement can be effectively utilized. While they have reactive silica, they may not have sufficient lime to produce pozzolanic compounds; another waste CL rich in calcium can be amended along with these solid wastes to soil to develop durable strength. Optimization of rice husk ash and bagasse ash contents is determined based on uncompressive strength tests. Strength tests carried out by mixing black cotton soil with various percentages of RHA and BA optimum dosages found are 20% and 15% for RHA and BA, respectively. Both RHA and BA are composed of silica content, and the strength improvement with respect to these additives without CL is marginal due to lack of lime content in them strength, thus enhancing considerably by adding carbide lime. Moulding water content also plays important role in pozzolanic stabilization. A series of strength tests were performed by mixing the black cotton soil with RHA, BA, CL and lime at different water contents and densities compacted with same compactive energy. The strength developed with moulding water content on dry side of optimum condition is more due to the existence of flocculated structure on dry side of optimum condition. The mechanism of strength improvement has been elucidated through microstructural analysis using SEM and XRD studies.KeywordsBagasse ashCompactionExpansive black cotton soilMineralsStructureUnconfined compression strength