Anytime the temperature drops below 70°, the setting of ready-mixed concrete slows down. This effect is most significant in the 30° to 50° temperature range, The rapid setting offered by the addition of calcium chloride to readymixed concrete allows concrete contractors to continue to work effectively into the fall and winter months.
In cool and cold weather concreting applications, calcium chloride can be used to reduce setting times by as much as two-thirds. A 2% admixture of calcium chloride at 50° will improve setting times to that attainable at 70° without calcium chloride.
This rapid setting can be critical when there is a chance that temperatures may drop below freezing. Calcium chloride accelerates the rate of hydration of freshly placed concrete and lowers its free water content faster.
This allows concrete to escape potential freeze damage in a matter of days, as opposed to the weeks it can take normally. And it minimizes the costly precautions required to protect freshly placed concrete from serious freeze damage.