Abstract: “The objective of this study was to select the best fly ash material which can replace river bed sand to fill underground coal mine voids. To achieve the objectives, this study examined the suitability of seven numbers of Indian fly ashes for filling in the underground coal mine voids based on their physicochemical, morphological and mineralogical characteristics. The physical properties such as bulk density, specific gravity, particle size distribution, specific surface area, porosity, moisture content, pH etc. have been determined. The chemical and mineralogical properties were also determined in the laboratory by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray fluorescence (XRF) studies. From the chemical characterization it is found that the fly ash samples are enriched predominantly with silica (SiO2), alumina (Al2O3) and iron oxides (Fe2O3) along with a little amount of CaO and all the seven fly ash samples”

Keywords: Fly ash, material characterization, mine void filling, specific gravity, density