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As indicated in Chapters 1 and 2, coal combustion products (CCPs) include fly ash, bottom ash, boiler slag (furnace bottom ash) and flue gas desulfurisation material (FGD). The latter, however, is not produced by Australian coal-fired power stations. Fly ash represents the largest component of the group, accounting for up to 90% of the CCPs produced. The fly ash is made up of fine (1.0-100 gm), powdery materials, composed of amorphous aluminosilicates and minor proportions of unburnt carbon. The texture of fly ash is comparable to that of soil (Adriano et al. 1980; Palumbo et al. 2004), with the majority of their particle size falling into the "silt and fine sand" texture range (Aitken et al. 1984). The chemical composition of fly ash generally reflects that of the parent coal while their physical features (size and shape) often make them suited as an alternative material in applications that use sand,gravel or gypsum. It is these general characteristics, elemental composition and physical properties, that have generated interest in their potential application for soil management in crop and pasture production systems in Australia and in many other parts of the world. |
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