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|Title:||Dependence of expansion of a salt-saturated concrete concrete on temperature and mixing and handling procedures|
|Authors:||Sandia National Laboratories.|
Wakeley, Lillian D.
Time of setting
Waste Isolation Pilot Plant
|Publisher:||Structures Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Technical report (U.S. Army Engineer Waterways Experiment Station) ; SL-87-20.|
Abstract: In experiments with an expansive salt-saturated concrete (ESC), time of setting was controlled by amount of sodium citrate used. The rheological and physical properties required of ESC were determined by its intended use, in an underground repository for radioactive wastes in bedded rock salt. These properties, including a long working time and low air content, could not be achieved using conventional high-range water-reducing admixtures, such as melamine or naphthalene formaldehyde condensates. Within a fixed range of citrate percentages, expansivity of the concrete was proportional to the amount of citrate used. The desired level of expansion resulted from delaying formation of ettringite until after formation of a rigid structure in the paste. Expansive potential was diminished by warmer temperatures of mixing curing, and by repeated episodes of mixing or disturbance during the extended period of workability (up to 4 hr). These variables should be considered in plans for field placement of this or any expansive concrete. The potential for durability of this concrete in the environment for which it was formulated cannot be gauged by those properties commonly used as indicators of durability for conventional concrete in surface environments. Low permeability and minimal reaction to brine are interrelated factors which may better indicate durability than do traditionally cited properties such as compressive strength or resistance to cyclic phenomena.
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