Compositions of belites in clinkers

Clinker belites typically contain 4-6% of impurity oxides, of which the chief ones are usually AI2O3 and Fe203. Correlations have been reported to exist between the MgO contents of belite and clinker (Kl), the Fe20, contents of belite and clinker (Kl), and the total impurity content of the belite and the MgO content of the clinker (B4). Early reports mention a compound KC23S,2, but the K2O content of 3.5% corresponding to this formula is well above those found in clinker belites, and recent electron optical work indicates that the limit of K2O substitution is about 1.2% (C1). 

In general, clinker belite compositions indicate ratios of other atoms to oxygen above the theoretical value of 0.75. As Regourd et al. (R3) noted, the C2S structures are too densely packed for the presence of interstitial ions to appear likely, and it is more probable that vacancies occur in the oxygen sites, with possible concomitant shifts in the positions of other atoms. Table 1.3 includes atomic ratios, with a possible allocation of atoms to sites. 

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