The proton free induction decay of a portland cement paste in an advanced stage of hydration can be roughly divided into three main components: (1) a component with a very short spin-spin relaxation time, T,, representing the protons of the solid OH groups and the water of crystallization, (2) a component with an intermediate T , representing the bonded water in the gel phase, and (3) a third component with a relatively long T2 representing the water in the micropores and layers. The dependences of the intensities, Tz's, and spin-lattice relaxation times (Ti's) of these three components on the cement hardening time have been determined. The proton spin-lattice relaxation time of the "solid" component increases with hardening time whereas T1 decreases for the other two components. The observed time dependence of the diffusion coefficient, D , of water in a tricalcium silicate paste supports the findings of the above correlation study.

The NMR spin-grouping technique is applied to low hydration oriented fibers of NaDNA to study the role of exchange in determining the apparent (observed) spin relaxation of the system. The analysis proceeds in three steps: first, the apparent proton relaxation is measured at high fields, with both selective and nonselective inversion pulse sequences, and in the rotating frame. The spin-grouping technique is used in all spin-lattice relaxation measurements to provide the optimum apparent relaxation characterization of the sample. Next, all apparent results are analyzed for exchange. In this analysis the results from the high field and rotating frame experiments (which probe the exchange at two different time scales) are correlated to determine the inherent (or true) spin relaxation parameters of each of the proton groups in the system. The results of selective inversion T1 measurements are also incorporated into the exchange analysis. Finally, the dynamics of each spin group are inferred from the inherent relaxation characterization. The low hydration NaDNA structure is such that the exchange between the protons on the water and those on the NaDNA is limited, a priori, to dipolar mixing. The results of the exchange analysis indicate that the dipolar mixing between water and NaDNA protons is faster than the spin diffusion within the NaDNA proton group itself. The spin-diffusion on the macromolecule is the bottleneck for the exchange between the water protons and the NaDNA protons. The water protons serve as the relaxation sink both at high fields and in the rotating frame for the total NaDNA-water spin bath. The inherent relaxation of the water is characteristic of water undergoing anisotropic motion with a fast reorientational correlation time about one axis (5 X 10(-10) less than or equal to tau r less than or equal to 8 X 10(-9)S) which is about three orders of magnitude slower than that of water in the bulk; and a slow tumbling correlation time for this axis (1.5 x 10(-7) less than or equal to tau t less than or equal to 8 x 10(-7)S) which is two orders of magnitude slower yet.

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The solidification of synthetic white cement is monitored by nuclear magnetic resonance. Proton signals in several different environments are resolved and the time evolution of their dynamics and relative numbers is presented. The amounts of liquid water (the water which has not yet entered the solid structure to become crystalline water) and Ca(OH)2 crystallites are monitored precisely during hydration. The technique gives a quantitative insight into the hydration process as well as the growth (and decay) pattern of various cement paste components.