What temperature must concrete be kept at for 72 hours?

• A. 10 C for 72 hours
• B. 20 C for 24 hours
• C. 5 C for 72 hours
• D. 15 C for 48 hours

Answer: (A)

Keeping concrete at an adequate curing temperature is crucial in the first days after pouring. Hydration—the chemical reaction that gives concrete its strength—happens best when the concrete stays warm enough and remains moist. If the temperature is too low, hydration slows, and if it drops low enough to freeze, the cement paste can be damaged and strength development is hindered.

The standard guidance for ensuring proper early strength is to maintain a temperature of at least 10 C (50 F) for 72 hours after pouring. This warmth supports steady hydration and minimizes the risk of freezing during curing, which helps achieve better long-term strength and durability.

Other options don’t fit because they either don’t maintain the required 72-hour duration or involve temperatures that are too low (risking freezing) or too high but for too short a period. So, keeping the concrete at 10 C for 72 hours is the best choice.