Fractionation and characterization of Texas lignite class ‘F’ fly ash by XRD, TGA, FTIR, and SFM

Fly ash is a complicated heterogeneous material and utilization of it requires a detailed knowledge of the physical and chemical characteristics. In the present study Texas lignite class ‘F’ ash was examined by X-ray diffractometer (XRD), thermogravimetric analyzer (TGA), Fourier transformed infrared spectrophotometer (FTIR) and scanning force microscopy (SFM). The XRD and FTIR data indicated that the bulk fly ash was composed of mullite, quartz, cristobalite and amorphous aluminosilicates. The TGA indicated a negligible amount of absorbed water, and an absence of structural water in the amorphous aluminosilicate phases. The magnetic component of the fly ash was made up of magnetite and present mostly in the coarser fractions ≥50 μm. The SFM of the bulk fly ash showed the presence of amorphous glassy surface and quartz. The fractionated samples indicated that about 90 wt% of the fly ash was composed of ≥50 μm particles. The amorphous component increased with the decreasing particle fractions. Hence, the chemical reactivity of fly ash will increase with the decreasing particle size.