Precise Determination of the 3CaO·SiO₂ Cells and Interpretation of Their X‐Ray Diffraction Patterns

Abstract

The cell dimensions of pure triclinic 3Ca0.Si02 and monoclinic 3Ca0 -SiOz solid solution (54Ca0. l6SiO2-Al2Oa.Mg0) were determined and the powder diffraction patterns were indexed by the method of precise measurement of the spacings. The lattice constants are expressed in terms of triclinic or monoclinic cells corresponding to pseudo-orthorhombic cells derived from Jeffery's trigonal cell. The apparent lattice constants for pure 3Ca0.Si02 are a = 12.195 a.u., b = 7.104 a&, c = 25.096 a.u., a = 90°, p = 89'44'' y = 89'44'; for 54Ca0.16SiO2.-ALOa.MgO, a = 12.246 a.u., b = 7.045 a.u., c = 24.985 a.u., @ = 90'04'. Precise lattice constants of Jeffery's monoclinic lattice for 54Ca0.-16SiOz-Al,Oa.MgO are derived as a = 33.091 a.u., b = 7.045 a.u., c = 18.546 a.u., @ = 94'08'. High-temperature X-ray patterns showed that pure triclinic 3Ca0 .Si02 transformed to a monoclinic form at about 920'C. and then to a trigonal form at about 970°C. Monoclinic 54Ca0.-16SiO2-AlZO3-MgO transformed to trigonal at about 830'C. These transitions were reversible and reproducible and were accompanied by only slight deformation of the structure forms.

Full-profile Rietveld quantitative XRD analysis of Portland cement: Standard XRD profiles for the major phase tricalcium silicate (C3S: 3CaO.SiO2)

“…Regourd (1964) studied polymorphism in pure C 3 S, Ca 3 SiO 5 , with high temperature X-ray powder diffractometry, and found six phases between room temperature and 1100°C. It is now known that there are seven polymorphs of C 3 S in this range -three triclinic phases to 980 °C, three monoclinic phases to 1050 °C and a rhombohedral phase above 1050 °C [Yamaguchi and Miyabe (1960); Bigare etal. (1967); Eysel and Hahn (1970); Maki and Chomy (1978); Regourd (1983); Eysel and Breuer (1983); Sinclair and Groves (1984); Takeuchi, Nishi, and Maki (1984)].…”

In situ synchrotron XRD measurements during solidification of a melt in the CaO–SiO2 system using an aerodynamic levitation system

“…The polymorphs can be distinguished in the angular ranges 32 to 33 °2θCu and 51 to 52 °2θCu by characteristic subcell reflections (Sinclair and Groves 1984). During cooling, the 2 ̅ 04 reflection of the trigonal cell at 32 to 33 °2θCu splits into the two 22 ̅ 4 and 4 ̅ 04 reflections of the monoclinic cell and during further cooling into the three reflections of the triclinic cell 224, 22 ̅ 4 and 4 ̅ 04 (Yamaguchi and Miyabe 1960). Similarly, one can observe this change at 51-52 °2θCu were 220 reflection of the trigonal cell splits into the 040 and 620 reflections of the monoclinic cell and later in the 040, 620 and 6 ̅ 20 reflections of the triclinic cell (Yamaguchi and Miyabe 1960).…”