Water transfers within Hemp Lime Concrete followed by NMR

The water transfers between the different phases of a Hemp Lime Concrete (HLC) were followed by NMR measurements. Due to the very different values of the NMR relaxation times of water contained in the different phases of the material the respective amounts of water within the hemp and in the mineral binder can be determined from an analysis of the time evolution of the distribution of T1 relaxation time of the whole sample. Reliable quantitative estimations in the different phases were obtained, as confirmed by the agreement between the total mass deduced from NMR and the weighted mass at any time. It is shown that for a sealed sample a significant water amount is initially absorbed in the hemp then progressively migrates towards the binder, which supplies additional water for the hydration reactions. For an open (drying) sample the same process occurs but a significant amount of water evaporates, and the hemp dries more rapidly than binder.