The exchange of hydroyene isotopes H and D between different linkage stages in concrete is experimentally followed tip. The measurements are carried out by Nuclear Magnetic Resonance (proton-NMH). A distribution between chemically bound and physically adsorbed water molecules is possible. The diffusion coefficient of water in concrete serves as a verification for tho D20 – H2O-content and is also measured by a NMR-methode. It can be shown that a extraction of chemically bound D20 by free H20 in concrete occurs at once at the moment of contact, but there are also exchange processes with large time constants.