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Acceptable Use of Calcium Chloride in Concrete

ASCC Position Statement #31


ACI 318-08, “Building Code Requirements for  Structural Concrete,” with some exceptions, allows calcium chloride as an accelerating admixture for cast-in-place concrete. But many specifications prohibit its use. This is unfortunate because calcium chloride is the most efficient and least expensive accelerator used in concrete. It is particularly useful when flatwork is placed in cold weather because both finishing and covering the slab with insulating blankets can be started earlier. Chloride accelerators also reduce the time required for curing and protection from freezing of structural concrete frames. Increasing the rate of early-strength development permits earlier removal of forms and earlier opening of construction.

Prohibiting use of calcium chloride accelerators is of special concern when project specifications for concrete require 20% to 50% of the portland cement to be replaced by fly ash. Using up to 50% fly ash replacement in cold weather increases costs because strength gain is slower and the duration of protection, which may include heating with fossil fuels, must also increase. 


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