Pore structure of hydrating cement paste by magnetic resonance relaxation analysis and freezing

Nuclear magnetic resonance relaxation analysis has been applied to interpret the evolution of microstructure in a cement paste during hydration, ii basic understanding of the wet-dry and freeze-thaw processes of cement pastes has been developed, The pore structure evolution has been studied by the suppression of the freezing temperature of water and compared with spin-spin relaxation analysis performed at room temperature, Both methods consistently show that hydrating cement pastes have two principal components in their size distribution, The NMR relaxation times provide a measure of the characteristic pore sizes, Their interpretation is made in the context of a fast exchange model. Supercooling and thawing point depression of confined water has been studied systematically, The depression of the freezing point of liquid water confined within a pore was found to be dependent on the pore size, with capillary pore water freezing at 240 K and the remaining gel pore water freezing over a temperature range extending to as low as 160 K, A modified Gibbs-Thompson analysis was used to determine pore volume distributions from the distribution of thawing temperatures. Copyright (C) 1996 Elsevier Science Inc.