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CPP: Chemische Physik und Polymerphysik

CPP 7: Dynamics of Molecular Systems

CPP 7.6: Vortrag

Dienstag, 3. April 2001, 18:25–18:45, 112

Cement hydration - solution and crystallization phenomena on the nm scale — •Nikolaus Nestle — Universität Leipzig, Abteilung GFP, Linnestraße 5, 04103 Leipzig

The hardening of cementitious materials is brought about by a complicated system of surface and liquid phase reactions taking place in an irregular, 3D nanostructured system. As this process is essentially a bulk phenomenon, the typical surface analytical techniques which are used in studies of reactions in 2D nanosystems are not appropriate for monitoring the course of cement hardening. A possible window towards these reactions is provided by proton NMR studies of the pore water in the cement paste. PFG-NMR experiments on the water self-diffusion behaviour and relaxation time measurements on hydrating cement pastes with various additives provide important informations on different steps of the hydration reactions. Among other interesting phenomena, an extremly strong isotope effect upon the addition of heavy water was observed as well as pronounced non-linear phenomena due to the action of so called superplasticizers, i.e. certain amphiphilic molecules that are used for conditioning the workability of concrete pastes. The observations are of interest both in order to identify controlling reaction steps under certain conditions and in order to plan additional studies on better-defined model systems.