STUDY ON SOIL - LIME - FLY ASH MIXES UNDER DIFFERENT COMPACTIVE EFFORTS FOR ECONOMIC USAGE IN ROAD CONSTRUCTION

Abstract

Fly ash is finely divided residue resulting from combustion of pulverised coal in thermal power stations. The ash produced in a power station consists of coarser fraction which falls to the bottom of the furnace (and hence called bottom ash) and light fraction of fine-ash (fly ash) which "flies" up the chimney and is collected •by the electrostatic precipitators. Fly ash is a waste product and poses serious • environmental problems if not disposed off properly. Fly ash when present alone has not any binding property but when mixed with lime, it poses pozzolonic properties. Fly ash reacts with free lime in the presence of water to form hydrated product of calcium and alumino silicates which have increased strength and durability and so fly ash can be utilized in the stabilization techniques of soil, when used with lime. It has been observed that fly ash, even in smaller amounts is beneficial in combination with lime in improving the strength of soils. The strength and stability characteristics of lime-fly ash stabilized soils are affected by type of soil, soil condition before use, type of lime, fly ash and their proportion in the mixture, lime reactivity of flyash, amount of compaction, compacting moisture content, uniformity of mix, type and period of curing. In the present work, an attempt has been made to study the strength characteristics of local Roorkee soil with fly ash and lime under different compactive efforts. CBR value & unconfined compressive strengths of different proportions of lime-fly ash - soil mixes, under different compactive efforts have been found out.