“…ASTM C 618 defines fly ash to be Class F if it contains at least 70 % of SiO 2 + Al 2 O 3 + Fe 2 O 3 [35] and according to this definition the fly ashes from Počerady, Mělník, Dětmarovice, and Ledvice are classified as Class F fly ashes. It can also be seen that all the fly ashes contain Si and Al in large amounts followed by Fe, Ca, K, Ti, Na, Mg, P, and Zr and various other trace elements like Bi, S, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, La, Ce, and Hg, as also determined by [36][37][38]. The fly ash from Počerady shows a high Si content and low Fe content compared to other fly ashes, which also indicates that Si is being replaced by Fe content in these fly ashes.…”