A phenomenological approach on the influence of paramagnetic iron in cement stone on 2D T1-T2 relaxation in single-sided 1H nuclear magnetic resonance

In recent years, there has been an increasing interest in H-1 nuclear magnetic resonance (NMR) relaxometry to obtain information on the hydration and porosity of cement stone. By spin-spin (T-2), spin-lattice (T-1), and combined relaxation studies, new insights were gained on liquid and crystal bound water as well as pore water exchange. A conversion of relaxation times to pore sizes has been developed and shown to give consistent results. In this study, we use single-sided H-1 NMR to obtain two-dimensional T-1-T-2 relaxation distributions on systematically varied cement stone samples as well as hydrated and solid cement phases. Results show a richness in features beyond past studies and are interpreted qualitatively in terms of water found in chemically different pore environments. Both T-1 and T-2 surface relaxivity of calcium silicate surrounded liquid water linearly correlate with the cement's Fe2O3 content. Results are discussed based on a theory of interacting surface relaxation mechanisms.