Curing in concrete continues until the relative humidity in the concrete drops below what percentage?

Curing in concrete is a critical process that helps ensure the strength and durability of the finished product. The process of curing involves maintaining adequate moisture, temperature, and time to allow hydration of the cement components within the concrete.

For effective curing, it is essential to maintain a relative humidity of the concrete throughout the curing period. Once the relative humidity drops below a certain threshold, the hydration process may be adversely affected, potentially leading to cracks and weaker concrete.

The correct answer is 80 percent. Curing typically continues until the relative humidity in the concrete falls below this threshold because, below this level, the hydration process is significantly hindered, risking the development of dry areas within the concrete.

While it is important to maintain a stable environment, thresholds lower than 80 percent can lead to improper curing and negatively impact the concrete's properties. The other options reflect relative humidity levels that are generally considered too high for the point at which curing can be effectively concluded, meaning the concrete still has the potential for ongoing hydration and strength development.

Maintaining relative humidity at or above 80 percent ensures that the concrete receives adequate moisture during the vital initial stages after placement, leading to improved structural integrity and longevity.