| Deuterium NMR relaxation experiments, low temperature deuterium NMR lineshape analysis, and FTIR spectra are consistent with a new model for solid state jump dynamics of water in 2H2O-synthesized kanemite, 2H2O-hydrated Na+-Zeolite A and 2H2O hydrated tricalcium silicate. Exchange occurs between two populations of water: one in which water molecules are directly coordinated to sodium ions and experience C2 symmetry jumps of their OH bonds, and a population of interstitial water molecules outside the sodium ion coordination sphere that experience tetrahedral jumps of their OH bonds. For both samples the C2 jump rate is much faster than the tetrahedral jump rate. 2H NMR relaxation experiments match well with the fast exchange regime of the model over a wide range of temperatures, including room temperature and above. For hydrated Zeolite A, the kinetic activation parameters for the tetrahedral and C2 symmetry jumps are DeltaHtet‡ = +17 kJ/mol, DeltaStet ‡ = -109 J/(mol K), DeltaHC2‡ = +19 kJ/mol, and DeltaSC2‡ = -20 J/(mol K). For kanemite, DeltaHtet‡ = +23 kJ/mol, DeltaStet ‡ = -69 J/(mol K), DeltaHC2‡ = +23 kJ/mol, and DeltaSC2‡ = -11 J/(mol K).;Additional evidence is shown that supports the hypothesis that a phase change of the water used for the hydration of tricalcium silicate is at least partly responsible for the initial hardening and strength gain of this type of cement paste. This process is shown to be reversible and fits well with other mechanical strength tests. |
