Regensburg 2016 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 73: Surface Dynamics: Reactions and Elementary Processes

O 73.10: Poster

Mittwoch, 9. März 2016, 18:15–20:30, Poster A

Investigation of Calcium-Silicate surfaces with UHV-IRRAS to understanding the first step in the corrosion of concretes — •Carsten Natzeck, Peter Weidler, Christof Woell, and Peter Thissen — Institute of Functional Interfaces, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

The well-oriented Calcium-Silicate substrate Wollastonite as our model sample is a chemically well characterized mineral (CaSiO₃). It has versatile physical properties for use in industry, reaching from medicine with the formation of artificial bones due to its bioactivity to construction chemistry with Calcium-Silicates (CS) as model system e.g. for cement and concrete. The surface chemistry of this CS substrate has been studied using infrared reflection-absorption spectroscopy under ultrahigh-vacuum conditions (UHV-IRRAS) using water and methanol as probe molecules. Exposure of the cooled substrate (100 K) to H₂O leads to the formation of surface OH-species. This proton transfer, which is a crucial step in the corrosion of concrete, is found to be absent when the same surface is exposed to methanol. These results are analyzed on the basis of a detailed, first-principles computational study employing densitiy function theory (DFT) and allow to derive a consistent picture on the chemical properties of this important mineral surface. Implications for corrosion protection of concrete in harsh environments will be discussed.