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Thoughts on the alite content and the
calculation of true phase contents in cement clinker
Dr. S. Chromy, Brno, Czech Republic
As a rule the true alite content of cement clinker is higher than the alite content calculated by Bogue. With the aid of regression analysis it is shown that this difference can be attributed to the combined effect of secondary elements and the degree of burning of the clinker. The secondary elements affect the stability fields of the clinker phases. As a result a local excess of SiO2 is formed in the belite fields during the formation of the alite and this decreases with the stage of distribution of SiO2 in the raw meal and with the decay of the reaction. The kinetic blocking by SiO2 causes a relative increase in the lime saturation and an excess of alite with respect to the equilibrium state that continues during the period of the reaction and only ceases after it ends. The findings obtained make it possible, with the aid of appropriate application of regression analysis, to calculate the true phase composition of the clinker from its chemical analysis. This phase composition is specific to the locality of the raw materials and forms a component of the complex calculation program for controlling and stabilizing the clink-er quality. Operational microscopy, a direct, independent, method for determining the true phase composition of the clinker is an essential check function in the operational application of this program. The results of the development of operational microscopy in recent years are described at the end of this article.
Summary CEMENT INTERNATIONAL 01/2006 pp 84-89
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