Effect of mechanical grinding on physical and chemical characteristics of circulating fluidized bed fly ash from coal gangue power plant

• We examine the characteristics differences between CFB-FA and OFA.
• The effects of mechanical grinding on the CFB-FA characteristics were investigated.
• The grinding efficiency of CFB-FA can be improved by organic grinding aids.

To characterize roles of mechanical grinding on the physical and chemical characteristics of circulating fluidized bed fly ash (CFB-FA), the differences between CFB-FA and ordinary fly ash (OFA) were revealed and the effects of mechanical grinding action on the physical and chemical characteristics of CFB-FA were studied from grinding kinetics, particle size distribution, bulk density, morphology, pore size distribution, amorphous substance content, anionic polymerization degree and hydration property and so on. The results indicate that there are some differences in chemical and mineral composition, particle morphology and self-hardening property between untreated CFB-FA and OFA. The particle size distribution of CFB-FA is optimized by mechanical grinding and the optimization role is best at 50 min grinding time. Mechanical grinding action can also reduce the interconnected pores, average pore radius, total cumulative pore volume and the pores content in range of greater than 3 nm radius of CFB-FA. Meanwhile, the amorphous substance dissolution amount of CFB-FA is increased and the polymerization degrees of [SiO4] and [AlO6] are reduced by mechanical grinding. All the 3d, 7d and 28d strengths of ground CFB-FA paste are improved significantly, and 3d and 28d activity index of the CFB-FA are also improved by more than 5% and 14%, respectively. Furthermore, organic grinding aids can further improve the mechanical grinding roles on CFB-FA and the role of ethylene glycol is the most excellent.