Quantitative Rietveld phase analysis of calcium aluminate cements

Rietveld analysis is a powerful technique for obtaining quantitative data on the relative amounts of phases in a mixture of phases, such as cement. However, a good knowledge of crystallography and the development of a refinement strategy with synthetic phase mixtures are essential to obtain reliable results. This paper describes the use of Rietveld analysis for a range of calcium aluminate cements. The series of cements studied illustrates well how complexity of analysis and the level of accuracy attainable depends on the complexity of the cement. In cements of high Al2O3 content, with very low concentrations of minor elements, the analysis is relatively straightforward and high levels of accuracy can be obtained. In cements of intermediate Al2O3 content the analysis is complicated by the formation of solid solutions, but good results are still achievable after development and testing of the refinement strategy with phase mixtures. In cement of lower Al2O3 content the mineralogy is complex due to the presence of significant amounts of iron. Nevertheless, the phases which have most impact on the reactivity of the cement can still be determined with a good level of precision.