Investigation of the hardening of cement-based materials with nuclear magnetic resonance (NMR)

Hydrogen nuclear magnetic resonance (1H NMR) is a direct method to determine the hydrogen content and with it the water content (moisture) in solids. Simultaneous it is highly sensitive probe of local, molecular-scale dynamical information in the 1 to 108 Hz frequency range, allowing to characterize structure molecular dynamics in hydrogenous liquids as well as in hydrogenous solids. Recent research results have demonstrated the extensive capability of NMR for characterizing structural properties in porous media. For a long time, NMR instrumentation was found only in laboratories of institutional and industrial research facilities. Meanwhile, for outside laboratory application and for nondestructive inspection of large objects special NMR devices are available, based on the one-sided access (OSA) NMR approach. Using this hardware type, many technologically valuable NMR applications could be transferred in nondestructive testing methods. This presentation will review the possibilities of OSA NMR for the characterization of porous solids, with a main focus to cementitious materials. The range of applications includes the depth-resolved determination of moisture profiles during wetting and drying of concrete, the investigation of specific surface and restricted diffusion in stones and the observation of cement hydration during concrete hardening. These applications will be discussed in the context of building inspection and geomechanical respectively petrophysical investigations.