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In today’s cement and concrete research, mineralogical quantification of (un)hydrated cement samples by X-ray Diffraction/Rietveld analysis becomes more and more important. As the results from XRD/Rietveld analysis are becoming increasingly more accurate, it became a widely used tool to study the hydration of cementitious materials besides other techniques e.g. isothermal calorimetry or thermogravimetric analysis. To quantify amorphous or non-identified phases, an internal standard might be added to estimate these so-called ‘other’ phases. Compared to unhydrated samples which are almost completely crystalline, it has a higher significance in hydrated samples, as certain cement hydrates, such as C-S-H, hydrogarnet, hydrotalcite, AFm, etc., are often poorly crystalline. Within the development of Completely Recyclable Concrete (CRC – a concrete designed for reincarnation within the cement production following the Cradle-to-Cradle Principle) the hydration of the regenerated cement was assessed by XRD/Rietveld analysis. Within this study it was found that the particle size distributions of the sample and the internal standard should not be underestimated within the quantification of the ‘other’ phases.

Although concrete is a durable material, it has a big impact on the environment due to its high production volumes. This impact is mostly related to the consumption of virgin raw materials, the production of waste and the emission of carbon dioxide. To optimize the recycling opportunities of concrete, Completely Recyclable Concrete is designed as a raw material for clinker production, without the need for ingredient adjustments. However, CRC concrete constructions may be exposed to environments rich in chlorides, sulphates and other ions, affecting the clinkering process of CRC rubble. Therefore, it is important to know the effect of these ions on the mineralogy of CRC clinker. In this study the effect of sulphate additions to CRC raw meals on the final clinker mineralogy was studied by XRD/Rietveld analysis. It was found that an increasing sulphate content stimulates the formation of CaO containing sulphates such as calcium langbeinite and anhydrite. Additionally SO3 was found to stabilize belite at the expense of alite.