Polymorphism of tricalcium silicate in Portland cement: a fast visual identification of structure and superstructure.

Mireille Courtial (1) , Marie-Noëlle de Noirfontaine (2) , Frederic Dunstetter (2) , Gilles Gasecki (3) , Marcel Signes-Frehel (3)

1 LAMH - Laboratoire d'Artois Mécanique et Habitat
2 LSI - Laboratoire des Solides Irradiés - Irradiated Solids Laboratory
3 CTG

So-called alite is a solid solution of tricalcium silicate Ca3SiO5 with a few percent of impurities. It constitutes the major phase of anhydrous Portland cement. In industrial compounds, alite crystallises into two monoclinic forms designated M1 and M3. The possibility of correlation between the crystallographic structure of the clinker and its reactivity is still an open question. The answer of such a question involves a proper quantitative analysis of the various phases –including the exact alite polymorph- of the industrial product. The rather similar structure of the two alites makes it difficult to distinguish them from their XRD patterns. This paper shows that five angular windows in the X-Ray diffraction patterns can be used with synthetic alites as well as industrial compounds, to identify the nature of the actual polymorph (M1 or M3) present and the structural model to be used (with or without superstructure) in subsequent Rietveld analysis of the data.

Mots clés: anhydrous cement; polymorphism; superstructure; X-Ray powder diffraction

Domaines: Cristallographie

Mireille Courtial, Marie-Noëlle de Noirfontaine, Frederic Dunstetter, Gilles Gasecki, Marcel Signes-Frehel. Polymorphism of tricalcium silicate in Portland cement: a fast visual identification of structure and superstructure.. Powder Diffraction, 2003, 18 (1), pp.7-15. ⟨10.1154/1.1523079⟩. ⟨hal-00278373⟩