Performance Enhancement of Expansive soil by Application of Fly ASH and Lime

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Expansive soils can imbibe large amount of water and undergo high volume changes, causing seasonal heave and shrinkage according to the availability of water. This often causes distress and failure of structures founded on such soils. Methods such as preloading, moisture control, replacement of affected soil, and additives have been used to deal with the swelling problems associated with these soils. Literature reveals that studies were conducted to modify the behavior of expansive soils using additives such as lime, cement, fly ash and other industrial wastes. However, not many studies have been performed on the combined application of lime and fly ash, particularly the non-self cementing fly ash, for treatment of expansive soils. In this research work, attempt has been made to study the geotechnical characteristics of expansive soil mixed with different composition of lime and fly ash. The main focus of this study is to find meaningful application of waste fly ash that does not qualify in construction industry and to use lime as an optimal modifier of properties wherever required. The geotechnical characteristics dealt in this study include plasticity, compaction, consolidation, swelling and strength. The variation of these properties due to combined addition of fly ash and lime has been systematically investigated. Here plasticity characteristics depict the modification reaction occurring in the soil mix where as the variation in strength characteristics indicate modification and solidification reaction. Therefore, effect of aging on these two parameters has been extensively studied. The undesirable effect of higher percentage of lime, over and above reported in the literature has been studied. It is noted that there is considerable influence of combined addition of fly ash and lime and aging on geotechnical properties of expansive soil. Some of the properties like plasticity and strength are influenced much by higher percentage of lime.The performance enhancement of expansive soil due to combined addition of lime and fly ash is clearly discussed and quantified in this study. Based on the results, suggestions have been made to maximize the utility of fly ash wherever possible. However, there are some chemical characteristics that need to be extensively investigated further for better explanation of certain trends observed in this study....
Supervisor: Sujit Kr Dash AND S. Sreedeep