Fluorides and fluorosilicates

the material was rhombohedral, even if cooled rapidly, and gave high 28-day strengths. In the presence of Al and F , C3S could be made by solid-state reaction at temperatures as low as 1025°C, though reaction was slow below 1050°C. At higher temperatures, F not lost by volatilization was mainly present in the melt, and thus acted as a flux rather than as a mineralizer. 

Another calcium silicate fluoride, cuspidine [Ca4(Si207)F2], exists but is not formed under conditions relevant to clinker formation. Systems containing fluorosilicate ions [SiF ] and the possible use of calcium fluorosilicate as a flux have been investigated (S16). 

In the Ca0-Al203-CaF2 system, the compound CiiA7-CaF2 was described in Section 2.2.3. One other ternary phase, of compositon 3CA CaF2, is known it is hexagonal, with a = 1.729 nm, c = 0.701 nm, and refractive indices co = 1.628, e = 1.618 (L7). Several studies on parts of the system have been reported (G22,C5,C7,Z4). 

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