Cell parameters. X-ray powder patterns and other data

5 Cell parameters. X-ray powder patterns and other data 

Regourd et al. (R3) synthesized several belites of P-C2S type with compositions similar to those found in clinkers and determined their cell parameters. With increased substitution, the crystallinity tended to decrease, causing broadening of XRD powder peaks. Two of their results are given in Table 1.5. 

Guinier and Regourd (Gl) summarized the thermal behaviour of C2S polymorphs. On heating, P-C2S shows endotherms beginning at 693°C and 1450°C, due respectively to the p - aY and oY - a transitions with y-C2S, the 693 C endotherm is replaced by a broad one beginning at about 748°C due to the transition to aY. The curve obtained on cooling a-CjS from 

modified by solid solution, occurs in nature as larnite. Early identifications of a -C2S with bredigite were incorrect (B9,M10). u-C S has been assumed to resemble nagelschmidtite (Ca7Si2P20,). but the unit cell of the latter seems to be more complex (Gl). 

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