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O: Fachverband Oberflächenphysik

O 60: Solid-liquid interfaces: Structure, Spectroscopy II

O 60.5: Vortrag

Mittwoch, 14. März 2018, 11:30–11:45, MA 144

Hydration of Concrete: The first steps — •Peter Thissen, Nicolas Giraudo, Carsten Natzeck, and Christof Wöll — Karlsruher Institut für Technologie (KIT), Institut für Funktionelle Grenzflächen (IFG), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

Concrete is the most important construction material used by mankind and, at the same time, one of the most complex substances known in materials science. Since this mineral compound is highly porous, a better understanding of its surface chemistry, and in particular the reaction with water, is urgently required to understand and avoid corrosion of infrastructure. We have gained insight into proton transfer from concrete upon contact with water by applying the so-called Surface Science approach to a well-defined mineral, Wollastonite. Data from infrared spectroscopy reveal that exposure of this Calcium-Silicate (CS) substrate to water leads to dissociation and the formation of OH-species. This proton transfer is a chemical reactions of key importance, since on the one hand it triggers the conversion of cement into concrete (a CSH phase), but on the other hand also governs the corrosion of concrete. Interestingly, we find that no proton transfer takes place when the same surface is exposed to methanol. In order to understand this unexpected differences, the analysis of the spectroscopic data obtained was aided by a detailed, first-principles computational study employing density functional theory (DFT). The combined experimental and theoretical effort allows deriving a consistent picture of proton transfer reactions occurring on CS and CSH phases.