Influence of Setting Accelerators on Chemical Shrinkage of Portland Cement

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Title: Influence of Setting Accelerators on Chemical Shrinkage of Portland Cement

Author(s): F. Clemmens, P. Depuydt, H. Justnes, D. Van Gemert, and E. J. Sellevold

Publication: Special Publication

Volume: 200

Issue:

Appears on pages(s): 235-250

Keywords: calcium chloride; calcium nitrate; cement paste; chemi-cal shrinkage; hydration; ions; portland cement; set accelerator

Date: 6/1/2001

Abstract:
The influence of a number of calcium salts on the total chemical shrinkage (used as a measure of cement hydration) of different portland cement pastes was followed during the first 48 hours. All calcium salts (acetate, chloride, formate, nitrate and nitrite) were added in an equimolar dosage of Ca’-corresponding to 1.5 % calcium nitrate by cement weight. An automatic Vicat-apparatus was used to monitor the setting time of the cement pastes. Experiments conducted at 5 OC, 13 OC and 23 OC revealed that calcium nitrate was the most effective set accelerator at lower temperatures and even more effective than calcium chloride at the lowest temperature. The anions of the different calcium salts were also found to influence the setting and the efficiency of each accelerator strongly depended on the cement type.