Mineral-based raw materials used for binder production usually contain a small amount of iron. While most of it is separated and removed when isolating MgO, traces of iron can remain in the binder. It is yet to be determined how such impurities affect HMC cement mixes and – when thinking of larger scales – the resulting concrete with its potential fields of application. Even low concentrations of an element can have a significant impact on cement and its hydration behaviour: what substances are formed, how quickly it hardens, how well it withstands mechanical stress, and how resistant it is to weathering. One part of the project tries to answer these questions by adding varying amounts of iron to high-purity, laboratory grade magnesium cement blends and mixing them with water. After hardening, the cement is analysed with state-of-the-art methods to shed light on its composition. Further experiments comprise the mechanical testing of mortar prisms with a hydraulic press to evaluate their resistance to loading. The other part of the project is carried out in cooperation with the Paul Scherrer Institute (PSI) and investigates the interaction between dissolved iron and magnesium cements. At the moment, knowledge on the corrosion of fortification in magnesium-based concrete is limited. Looking at the behaviour of the corrosion products can help gaining a better understanding of their mobility. The implications of those experiments are not solely limited to the mobility of corrosion products but can also help to make a first assumption on the suitability of magnesium-based cements as repositories for radioactive waste.

Contact: Jan Schmitt, Barbara Lothenbach

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