[en] The exchange of hydrogen isotopes H and D between different binding states in concrete has been investigated experimentally with the aid of nuclear magnetic resonance (proton NMR) measurements. The distinction between chemically bound and physically adsorbed water molecules has been possible. The diffusion coefficient measured by NMR was used for detecting the D₂O/H₂O mixture. It could be shown that the extraction of chemically bound D₂O by free H₂O in concrete occurs at once at the moment of contact, but that there are also exchange processes with large time constants