The analysis showed that the composition of the original ash sample included mainly quartz, lime, anhydrite, calcite and smaller amounts of orthoclase, periclase, gehlenite
, larnite, merwinite, pseudowollastonite, hematite, ettringite, melilite and dolomite (Table 2).
The main crystallographic phases in the fly ash pattern are quartz (d = 3.34 [Angstrom]), cristobalite (d = 4.04 [Angstrom]), feldspars (d = 3.19 [Angstrom]), gehlenite
(d = 2.85 [Angstrom]), maghemite (d = 2.52 [Angstrom]), and anhydrite (d = 3.49 [Angstrom]).
Ma, "Ca 2+ and OH--release of ceramsites containing anorthite and gehlenite
prepared from waste lime mud," Journal of Environmental Sciences, vol.
Above 850[degrees]C, the decomposition of calcite can give rise to high-temperature calcosilicates and alumino-calcosilicates, member of the pyroxene group, such as the diopside, plagioclase feldspars (anorthite), gehlenite
and wollastonite (Papachristodoulou et al.
A range of products is formed, including CSH, [C.sub.2]AS[H.sub.8] (gehlenite
hydrate) and hydrated calcium aluminates, [C.sub.4]A[H.sub.13] and [C.sub.3]A[H.sub.6] [21, 22, 23].
Slag consists of calcium magnesium silicate (akermanite) and calcium aluminium silicate (gehlenite
) (Li and Gilkes 2002).
The following standards were used: sanidine (K K[alpha]), cuprite (Cu K[alpha]), diopside (Ca K[alpha]), nichromite (Ni K[alpha]), zincite (Zn K[alpha]), synthetic [Cd.sub.5][([PO.sub.4].sub.3](OH) (Cd L[alpha]), gehlenite
(Al K[alpha]), synthetic V[P.sub.2][O.sub.7] (V K[alpha]), apatite (P K[alpha]) and phlogopite (F K[alpha]).
It shows the existence of a large peak in the 29 range of 20-38[degrees] and a very small amount of the gehlenite
phase without any distinct crystalline peaks.