Effect of lithium, strontium and barium carbonates on the belite phase formed at 1200°C

A reference belite is prepared from burning calcite and quartz (mole ratio= 2), 1.5 hours at 1200°C. The belite polymorphs formed in presence of Li2CO3 with 1% Li2O, as fluxing and doping agent, in addition to SrCO3 and BaCO3 with amounts equivalent to 8% SrO and 8% BaO, as mineralizers, are identified. The thermal behaviors of the belite mixes and of the pure carbonates are recorded for temperatures up to 1300°C. The polymorphs formed are defined by means of X-ray Rietveld analysis, and are examined under a scanning electron microscope. It is found that the beta and gama polymorphs are equally formed in the belite doped with strontium, and in presence of barium, the alpha’ appears as well. The decomposition of Li2CO3 to Li2O is depressed by strontium and barium carbonates due to the increase in the partial pressure of CO2 and consequently the melt is stabilized. .Further research is needed to explain the effect of CO2 partial pressure of the carbonates on the polymorphism of belite.