Tricalcium silicate polymorphs

Tricalcium silicate is the most important component of Portland cement clinker. Its share as a rule is overpassing 55% and reactivity with water has the decisive effect on paste hardening. At room temperature CjS is triclinic. The structures of different polymorphic phases of tricalcium silicate was determined by Jeffery [99], The basis was the rhombohedral pseudo-stracture with hexagonal unit cell [99] ... 

Also in 1965, Ono, Uno, and Kanai reported data on five laboratory-made polymorphs of tricalcium silicate that persisted at room temperature. These authors described monoclinic, triclinic, and rhombohedral forms of alite. 

Nurse, R.W. Midgley, H.G. and Welch, J.H., Polymorphism of Tricalcium Silicate and Its Significance in Cement Hydration, Great Britain Department of Scientific and Industrial Research, Building Research Station, Note A95,1961,10 pp. 

Tricalcium silicate exists in several polymorphic forms. It can be triclinic, monoclinic, or trigonal. The stability of pol miorphs and their transitions are temperature dependent and not easy to determine because many forms have small transition enthalpies. The triclinic form (Tj) can be stabilized with chromium oxide, the triclinic form (Tjj) by ferric oxide, the monoclinic form (Mj) by MgO and monoclinic (Mjj) form by zinc oxide. The monoclinic form is present in commercial clinkers and only rarely has the rhombohedral form been detected. 

Ramachandran, V. S., Estimation of Tricalcium Silicate Through Polymorphic Transition, J. Therm. Anal, 3 181-190 (1971)... 

De Noirfontaine, M.-N., M. Courtial, E Dunstetter, G. Gasecki and M. Signes-Frehel (2012). Tricalcium Silicate Ca3SiOj Superstructure Analysis A Route towards the Structure of the Ml Polymorph . Zeitschrift fiir Kristallographie 227 102-112. 

Peterson, V. K., B. A. Hunter and A. Ray (2004). Tricalcium Silicate T1 and T2 Polymorphic Investigations Rietveld Refinement at Various Temperatures Using Synchrotron Powder Diffraction . Journal of the American Ceramic Society 87 (9) 1625-1634. 

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