At the last CALPHAD meeting we reported on some of the difficulties experienced in the prediction of the phase constitution and composition of cement clinkers. These were primarily associated with the inadequacy of the data for solid solutions in the principal constituent phases.
A database for the solution of a range of elements in Hatrurite (tricalcium silicate) has now been developed on the basis of French experimental studies. This has been used in association with solution data for dicalcium silicate, tricalcium aluminate, dicalcium ferrite and oxide liquid available in MTOX to predict (a) the form of isothermal ternary sections through the CaO-Al2O3-SiO2-MgO-Fe2O3-K2O-Na2O system at fixed values of MgO, Fe2O3, K2O and Na2O typical of the composition of Portland Cements and (b) liquidus contours. Discrepancies between the distribution of the minor elements among the cement phases are discussed in terms of kinetic considerations and the reliability of the available thermodynamic data.In addition to the phase diagram studies, a limited number of predictions have been made of the solution of Zn released from such fuels as car tyres into the cement phases and are discussed in relation to laboratory studies of the solution of zinc in cement clinker.
E-mail: k.g.ahari@sheffield .ac.uk