Cold Water Concrete: which conditions are listed for its use?

• A. Three consecutive days below 40 degrees
• B. Twelve of the twenty-four hours prior to pour below 50 degrees
• C. Both of the above
• D. None of the above

Answer: (C)

When cold weather concreting procedures are required is based on temperature history. Two scenarios trigger the measures: a sustained spell of cold—three consecutive days with temperatures below 40°F—and a recent chill that can still affect early strength—twelve of the twenty-four hours prior to the pour with temperatures below 50°F. If either condition occurs, protective steps are applied to keep the concrete from freezing during early curing, such as heated or insulated materials, enclosures, and controlled curing methods. Since both conditions are valid triggers, the correct understanding is that both are listed for use.