The main objective of this project is to develop an elementary physical/chemical bridging model for the initial dissolution mechanism of alite and belite cement clinker hydration that connects the nanoscale to the upscaled microscale level. The approach starts with an in-depth understanding of alite and belite clinker surfaces by atomistic modelling of the surface complexation and far-from-equilibrium dissolution while differentiating between the various crystal planes. The upscaled model will quantify and validate the net dissolution rates, as an essential process which later has to be considered by models attempting to capture the kinetics of cement hydration. The multiscale model will enable a deeper understanding of the alite and belite reactivity by predicting the dissolution rate as a function of the interplay between the mineral crystal structure and the chemistry of the surrounding solution. This understanding will allow new optimization routes for cement and cement replacing phases whose sustainability potential is directly impeded by their low reactivity. The sustainability of cementitious binders can be enhanced by the reduction of the clinker content without loss of hydration performance.To achieve the main objective, a multiscale model will be developed at different scales by the two groups of the University of Kassel (UniKs) and the Technical University of Darmstadt (TUDa). UniKs will couple a biased molecular dynamics (MetaD) model with a reactive force field (ReaxFF) to obtain reaction paths and activation energies. The calculated rate constant of all atomistic reaction steps will be provided to TUDa group for developing the upscaled model using a kinetic Monte Carlo (kMC) method.In the project, the following stages will be considered, representing the sub-objectives: a) Evaluating the reactivity of different crystal planes of alite and belite; b) Obtaining of atomistic reaction paths and activation energies for far-from-equilibrium solutions; c) Upscaling the atomistic rates of alite and belite dissolution, employing a kinetic Monte Carlo (kMC) approach; d) Investigating the effect of higher saturations in the surrounding solution on kMC results e) validation of c) and d) by literature experimental data.First, the kMC upscaling dissolution rates will be validated on far-from-equilibrium conditions. This is of major importance, as it will enable a separation of the individual contributions of the combined dissolution-precipitation reaction processes for a better prediction and interpretation of the experimental research. Next, validation of kMC predictions with experimental results will consider the effect of higher saturation of the surrounding solution, to gradually approach realistic conditions for the initial cement hydration process.
- Professor Dr.-Ing. Eduardus Koenders, Ph.D.
- Technische Universität Darmstadt
- Institut für Werkstoffe im Bauwesen
- Professor Dr. Bernhard Middendorf
- Universität Kassel
- Institut für konstruktiven Ingenieurbau (IKI)
- Fachgebiet Werkstoffe des Bauwesens und Bauchemie
Subject Area: Construction Material Sciences, Chemistry, Building Physics
Project identifier: Deutsche Forschungsgemeinschaft (DFG) – Project number 455605608
Term: since 2021
DFG Programme: Research Grants
Co-Applicant: Dr.-Ing. Neven Ukrainczyk, Ph.D.