High-calcium fly ash middlings of brown coal of B2 (sub C) rank from the Berezovsky coal mine within the Kansk-Achinsk Basin were studied. The middlings were selectively sampled from the convection pass, the fore-hearth and each of the 4 fields of the electrostatic precipitator at the coal-fired power plant BSDPS-1. The differences of the dispersity, the chemical and mineral-phase composition and the cementing properties of these middlings, as well as the types in the ash classification system were determined. Within the ternary CaO-SiO2-Al2O3 diagram, the equilibrium phases composition of the aluminosilicate constituent of middlings and the pozzolanic capacities of glasses of this system were analyzed and compared with the actual phase composition. It was concluded that the fly ash middlings of the 4 fields of the electrostatic precipitator have the best prospect of utilization as component of cementing materials including portland cement and belite-sulfoaluminate cement. (C) 2010 Elsevier B.V. All rights reserved.