129. CBR Values of Stabilised Fly Ash

The successive five year development plans in the country were formulated in such a way as to favour more intensive and rapid expansion of heavy industrialization, which requires great amount of electric power. Most of the power plants in different parts of the country are coal based, producing a large amount of fly ash (about 110 million ton per annum) as a waste by-product. The Indian coal has high ash content varying from 30–50 per cent and low calorific value. As the disposal of fly ash requires large areas, it is important to have its bulk utilization as in base and sub base of the road, embankments, backfills etc., so as to increase the ash utilization in the country. Conversion of inherently present mineral matter of coal into fly ash is the natural outcome of the combustion of pulverized particles of coal at temperature in the range of 1300–1450 ^OC. It is the ligher variety of fine ash, which flies up the chimney with flue gases and is collected either mechanically or by electrostatic precipitators. It contributes about 75–85 per cent of the total ash produced. The nature and quality of fly ash depends upon a number of factors like, the mineralogical characteristics of coal, fineness of grinding of the coal, nature of combustion system, type of burners, air/fuel ratio and types of precipitators used. The fly ash has low strength and generally not suitable for use in road construction either in subgrade or subbase. Earlier studies have been made on engineering behaviour of fly ash when stabilized with lime. For bulk utilization of fly ash, the amount of lime needed will be enormous and mixing too is a tough job. The major objective of this study is to stabilize the fly ash with fine sand and to observe the changes in its Proctor's density and CBR values.