title: Pore structure of hydrating cement paste by magnetic resonance relaxation analysis and freezing.
abstract: Nuclear magnetic resonance relaxation analysis has been applied to interpret the evolution of microstructure in a cement paste during hydration. A 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.
authors.affiliation: Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA.
authors.forename: J Y
authors.initials: JY
authors.lastname: Jehng
authors.forename: D T
authors.initials: DT
authors.lastname: Sprague
authors.forename: W P
authors.initials: WP
authors.lastname: Halperin
mesh_terms: D003252:Construction Materials; D005615:Freezing; D009682:Magnetic Resonance Spectroscopy; D016062:Porosity; D014867:Water
chemical_list: D014867:Water