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Suspended Hydration and Loss of Freezable Water in Cement Pastes Exposed to 90% Relative Humidity



Kenneth A. Snyder, Dale P. Bentz


Degree of hydration and differential scanning calorimetry (DSC)measurements characterize the effect of a 90 % relative humidity (RH) environmental exposure on early cement paste hydration. Cement paste specimens 1.6 mm thick and with water-cement mass ratios ranging from 0.30 to 0.50 are initially exposed to a saturated environment and then exposed to a 90 % RH environment after varying curing intervals. As expected, specimens exposed to the saturated environment for a sufficiently long time prior to 90\% RH exposure where indentical to specimens hydrating in saturated conditions. Early exposure to 90 % RH, however, can remove sufficient free water to halt hydration, and prolonged exposure leads to water loss in pores that would otherwise be saturated when exposed to a 90 % RH environment. The duration of saturated exposure required for an unsaturated environment to have no effect appears to be related to the time required for cessation of capillary pore percolation.
NIST Interagency/Internal Report (NISTIR) - 7063
Report Number


building materials, cement, concrete, curing, degree of hydration, moisture


Snyder, K. and Bentz, D. (2004), Suspended Hydration and Loss of Freezable Water in Cement Pastes Exposed to 90% Relative Humidity, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed June 14, 2024)


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Created October 31, 2004, Updated October 12, 2021