ACI Concrete Field Testing Technician - Grade I Practice Exam

Keeping concrete cylinders moist during curing is essential primarily to prevent cracking and ensure proper hydration. Concrete gains strength through a chemical reaction known as hydration, which occurs when water interacts with the cement. If the concrete dries too quickly during this process, it can lead to insufficient hydration and ultimately result in weakness and cracking.

Maintaining moisture creates a controlled environment that allows the hydration process to continue for a longer period, typically recommended for at least 7 to 14 days. This ensures that the concrete achieves its intended compressive strength and durability. Proper curing also helps to minimize the risk of surface defects that arise from rapid moisture loss, which can compromise the integrity of the structure.

While some options mention aspects related to the handling and properties of concrete, they do not address the critical role moisture plays in the curing process and hydration specifically. Therefore, the emphasis on preventing cracking and ensuring proper hydration defines the importance of keeping concrete cylinders moist during curing.