Comprehensive chemical- crystallographic characterization of Portland cement clinker is an important prerequisite in order to understand reactivity of cements and thus the properties of concretes.<br/>State of the art in clinker characterization is that various spectroscopic methods are applied to powdered bulk samples to measure chemical composition. On the basis of this data and by assuming stoichiometric composition the phase fractions are calculated. Another way is to use powdered clinkers for quantitative X-ray diffraction analysis. Thereby also crystallographic information is obtained. A main disadvantage of all these analytical methods is that they are carried out on bulk powders, i.e. no spatially resolved chemical-crystallographic characterization is available. In a technical multi-phase mixture such as Portland cement, it is up to date difficult to demonstrate changes in the crystallographic properties of individual clinker phases in dependence of variation in chemical composition. Unraveling the interaction between clinker phases major, minor and trace element content (due to variation in raw materials and fuel composition) on crystallographic properties and reactivity of cements is a major challenge in cement and concrete research .<br/>The advantage of materials characterization in the scanning electron microscope (SEM) is that it takes place spatially resolved. If one combines electron backscatter diffraction (EBSD) with energy dispersive X-ray (EDX) spectroscopy in the SEM a spatially resolved chemical - crystallographic characterization is obtained. If furthermore these analyzes are recorded as mappings it is possible to get quantitative evaluation.<br/>However, EBSD must obtain analyzes of clinkers at undisturbed crystal lattice at the sample surface (information depth of the diffraction signal is about 50 - 100nm). Conventional polishing techniques applied for EBSD on metal, stone and ceramics fail for cement clinker. Results of the present study show that argon broad ion beam polishing can be used for cement clinker EBSD sample preparation. Furthermore it is shown that coupled EDX-EBSD mappings on cement clinkers can be used to analyze chemical composition of all clinker phases and to detect grain boundaries as well as crystallite size of crystalline clinker phases. Also EDX-EBSD analysis is able to identify amorphous clinker phases.<br/>Finally the new EDX-EBSD results are compared to traditional microscopic clinker characterization.

Characterization of Portland cement clinker by Electron Backscatter Diffraction (EBSD) analysis in the Scanning Electron Microscope (SEM)

253rd National Meeting (2017)

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