Calculations of Portland cement clinkering reactions

Calculations have been undertaken of both equilibrium and non-equilibrium chemistry of relevant parts of the CaO—Fe₂O₃—Al₂O₃—SiO₂ system and related reactions in the gas phase. The examples provide new insights into topics of current concern in the manufacture of Portland cement, including the early stages of melting, the undesirable retention of lime, the ferrous iron content and the phases formed during non-equilibrium cooling, their proportions and composition. The proportion of the C₃S (alite) phase depends exclusively on the early stages of cooling, when neither ferrite nor C₃A is present. This and the fact that the phases do not have fixed compositions illuminate the limitations of the Bogue calculation for estimation of C₃S. Calculations involving the gas and liquid salts are used to investigate reactions of sodium and its build-up in the hot zone of the kiln. The scope and limitations of the database and methods for calculations on these processes are discussed.