Rietveld Mineralogical Analysis of Portland Cements

Abstract

There is a great interest in the Quantitative Phase Analysis (QPA) of complex crystalline mixtures such as clinkers or cements. Final performances of these materials mainly depend on their mineralogical compositions and textures and not on the elemental compositions, as determined by x-ray fluorescence, XRF. X-ray Powder Diffraction (XRPD) combined with the Rietveld method is the most powerful tool to obtain the QPA of the cement samples. Here, we present mineralogical analyses for white Portland clinkers, gray Portland clinkers and gray Portland cements, using laboratory XRPD and the Rietveld method. The complexity of the systems is variable with the easiest mixture having three crystalline phases. Nevertheless, the toughest case can contain up to nine phases. Some effects such as good/poor particle statistics, preferred orientation or microabsorption have to be borne in mind in order to get accurate results. So, data collection strategy is very important. Moreover, it is possible to quantify the amorphous/non-diffracting content of the building materials by adding a suitable standard, for example Al2O3. Some results and guidelines to carry out the refinements of these mixtures will be given.