Polymorphism of Tricalcium Silicate, the Major Compound of Portland Cement Clinker: 1. Structural Data: Review and Unified Analysis

This paper reviews the literature devoted to structural investigations of the polymorphism of tricalcium silicate, the major compound of Portland cement clinker, with a special concern to the various notations used by different authors. Anhydrous Portland cement is essentially made of a synthetic rock (clinker) which contains at leasat four major phases. Alite and belite are two solid solutions of two calcium silicates, with a few impurities. Two calcium aluminate phases are also observed: they constitute an interstitial phase between the larger crystals of both silicates. A unified analysis of the known T1, M1, M3 and R polymorphs is proposed. The superstructure relations between the various unit cells are discussed, together with the evidence of common 1D and 2D structural elements in all these polymorphs. These structural elements are related to the observed properties.