Recovery, processing, and usage of wet-stored fly ash

With changes in how electricity is generated, there may be a gradual reduction in available fly ash for use in concrete and other applications. The significant quantities of fly ash stored around power plants in stockpiles and ponds, in some cases over many years, represent a source of material that could help address this situation. Wet-stored fly ash can undergo physical and chemical changes during storage, affecting its reactivity potential and it may be prone to variability. Recovery of this is therefore likely to involve evaluation of the material properties, and development of processing strategies. This chapter examines (i) the characteristics of wet-stored fly ash, (ii) methods of sampling material, (iii) various wet processing techniques that can be used to remove or concentrate components, and (iv) use in cementitious systems. Consideration is also given to the direct use of conditioned/stockpile fly ash in concrete.