Characterization and control of ettringite morphology to master the rheology of cementitious systems (EMORPH)

• Applicants: Professor Dr. Torben Gädt; Dr. Christiane Rößler; Dr. Wolfram Schmidt
• Subject Area: Construction Material Sciences, Chemistry, Building Physics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 562957920

The EMORPH project aims to deepen our understanding of ettringite formation in the context of the rheological properties of fresh concrete. The project will investigate how the amount, spatial distribution and morphology of ettringite influence the rheology of cementitious systems. Particular attention will be paid to the interactions between C3A, sulfate agents, PCE superplasticizers and external aluminum sources such as calcined clays. In the project, new methods are established to characterize the size, shape, quantity and distribution of ettringite in the early hydration phase. The combination of scanning and transmission electron microscopy plays a crucial role in precisely describing the shape and distribution of the ettringite. Ettringite parameters such as size, quantity or surface area are quantified for both model and cement-based systems. The aim is to investigate in detail how the variation of the superplasticizer chemistry on the one hand and the variation of the binder chemistry on the other hand contribute to different ettringite parameters. In addition to the micro- and nanoscale description of the ettringite phases, the colloidal and rheological properties of granular suspensions are investigated. In-situ rheomicroscopy is used to document the shearing of ettringite particles and linked to rheological measurements on cement suspensions. Systematic variation of the suspensions allows the determination of yield point, viscosity, but also statements about percolation volume and time as a function of the ettringite parameters. The aim is to refine the existing rheological models with regard to the ettringite parameters. The combination of experimental data and rheological measurements should provide a deeper understanding of the role of ettringite formation in relation to the rheology of fresh concrete. All results will be used in model approaches. This knowledge is particularly valuable in the context of low-cement-clinker binders, in order to maximize the resource efficiency of the binders and minimize the CO2 intensity.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Professor Dr. Nicolas Roussel