Strength and Permeability Characteristics of Indian
Coal Ashes

Abstract

Coal is the major source of electricity generation in India. 72% of the country’s coal production is consumed by electricity sector. These coals have high ash content and low calorific value. The combustion of coal in the thermal power plant results in the generation of coal ashes i.e. fly ash and bottom ash. The present study is related to the study of geotechnical properties, permeability and strength characteristics and finding its suitability in geotechnical fields in bulk. Coal ashes were collected form three different thermal power plants in India and laboratory tests were done. Specific gravity was calculated. Hydrometer test was carried out for the grain size distribution. MDD (g/cc) and OMC (%) were found out at four different energy levels. Direct shear test at standard compaction and UCS at standard and modified compaction was done to find out the strength parameters. SEM and XRD analysis was done to deduce the morphology and mineralogy of the coal ashes. The falling head permeability test at 95% MDD and 100% MDD at four different energy levels was performed to find out the coefficient of permeability. The consolidation test was also performed to study the swelling and compressibility characteristics. Quartz, mullite were the dominant mineral present. The fly ash consisted of rounded, sub-rounded and solid spherical glassy particles. Bottom ash particles were relatively bigger than that of fly ash. They possessed low G value, low compressibility, high friction angle and k value in the range of silts.