Suspended Hydration and Loss of Freezable Water in Cement Pastes Exposed to 90% Relative Humidity.
Suspended Hydration and Loss of Freezable Water in
Cement Pastes Exposed to 90% Relative Humidity.
Snyder, K. A.
Cement and Concrete Research, Vol. 34, No. 11,
2045-2056, November 2004.
cement pastes; hydration; water; humidity; calorimetry;
Degree of hydration (DOH) and differential scanning
calorimetry (DSC) measurements are used to characterize
the effect of early exposure to a 90% relative humidity
(RH) environment on cement paste hydration. Early
exposure to a 90% RH environment can lead to the
consumption of freezable water and altered
microstructural development. The minimum duration of
100% RHcuring required to eliminate the effects of an
unsaturated environment on microstructural development
coincides with the appearance of a DSC peak near -30 deg
C that occurs in the range 1-14 days for the pastes
studied. The Jennings colloidal microstructural model is
used to argue that the -30 deg C peak coincides with the
cessation of capillary pore percolation. Alternatively,
all samples cured under 100% RH conditions for 7 days
prior to 90% RH exposure hydrated at the same rate as
those continuously exposed to 100% RH. The application
of these results to the formulation of separate curing
practices for durability and strength is discussed.