Caracterisation of Cement Microstructure and Pore-Water Interaction by 1H Nuclear Magnetic Resonance Relaxometry.

1H nuclear magnetic resonance (NMR) relaxometry is used to characterise cement paste microstructure from the stand point of the pore water. Attention focuses primarily on pore-water interactions and the morphology of calcium-silicate-hydrate (C-S-H), the active phase of cement paste. The method is non-destructive and non-invasive. NMR allows the quantitative separation of water by confinement. The first pore-type resolved sorption isotherm of any cementitious material is measured. This provides insight into water location during drying and wetting. The C-S-H interlayer and gel pore sizes are estimated based on T2 relaxation times (0.94 ± 0.04 and 3.1±0.2nm) and amplitudes of relaxation components during drying (1.5 ± 0.3 and 4.5 ±1.6 nm). The specific surface areas are also evaluated. The evolution of nanoscale porosity for underwater cured white cement pastes, with and without silica fume addition, are determined during hydration and as a function of temperature in the range 10°C to 60°C. The C-S-H density and chemical composition are evaluated using NMR supported by X-ray diffraction and thermogravimetric analysis. The calculated C-S-H ‘solid’ density and composition, excluding gel pore water, in never-dried 28 days old white cement paste are 2.64 ± 0.03 g/cm3 and Ca1.53±0.02(Si0.960. 01,Al0.04±0.01)03.51±0.02(H2O)1.92±0.05. The C-S-H ‘bulk’ density, including gel pore water, is 1. 90±0.02 g/cm3. Increase of curing temperature does not alter the Ca/(Si+Al) ratio. However, a significant decrease in C-S-H water content and increase in density is observed and attributed to the fewer locally stacked C-S-H layers. NMR relaxation activation energies are estimated. Insight into the mechanism of water-isopropanol exchange, used for arresting cement hydration, is provided. NMR shows that the exchange occurs in a selective manner with no C-S-H interlayer water alteration. The connectivity of the C-S-H interlayer and gel pores with interhydrate-capillary pores is evidenced