Qualitative and quantitative chemical-mineralogical characterisation of Portlandcement clinkers by means of scanning electron microscopy techniques

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In the previous project, the EBSD method for the characterization of cement clinkers was established. As described in the project report, the coupled EBSD-EDX analysis offers for the first time the possibility to characterize cement clinker in a spatial-resolved chemical-crystallographic manner. This means that for all clinker phases their fraction, chemical composition (including minor and trace element), crystallinity and crystallite sizes can be determined. For the first time crystallite sizes of the fine-grained clinker phases are accessible (1-10 μm).In the continuation of the project, the EBSD-EDX technology, previously successfully established in the cement sector, will be further developed to enable high-resolution, statistically safe analyzes of all clinker phases. A new, high-resolution EBSD camera is to be used for this purpose.Belit: In the previous project, it was found that the EBSD patterns of belite indicate low crystallinity, and that even when they are observed in idiomorphic crystal shape only very small crystalline areas can be detected. With the help of a more sensitive, high-resolution EBSD camera, the fine structure of the belite in Portland cement clinkers is to be analyzed in the follow-up project. In addition, alternative, climate-friendly clinkers are also to be characterized, in which a variability of the belite crystallinity is suspected. These are clinkers based on belite calcium-sulfo-aluminate-ternesite (BCT) and belite ye'elemit ferrite (BYF), which have not yet been characterized by EBSD-EDX.Alit: In the first part of the project, coupled EBSD-EDX analysis has already been successfully used to characterize the chemical-crystallographic composition (phase fraction, chemical composition, and crystal size) of various alite modifications. With the new EBSD camera, the influence of foreign ions on the fine structure and performance of alites is to be investigated systematically.Calcium aluminate (C3A) and - ferrite phases (C4AF): For these phases fundamental chemical-crystallographic analyzes have hitherto only been possible to a limited extent. In particular, the influence of the variation of the crystallite sizes and the chemical composition on the reactivity of the phases is still controversially discussed. In the proposed project, the high-resolution chemico-crystallographic characterization of C3A and C4AF phases contained will be optimized. Especially the structural changes of C3A and C4AF phases induced by variation in iron, magnesium and alkali content of cement clinker will be studied. All characterizations are to be accompanied by hydration studies in order to allow the correlation of the data obtained with the reactivity of the materials.As a result of the project, the coupled EBSD-EDX clinker analysis will be practical applicable and basic relations between clinker phase composition, crystallinity and reactivity will be revealed.