What type of water shall be used in C511 curing methods?

The correct choice for the type of water to be used in C511 curing methods is water saturated with calcium hydroxide. This requirement is specified because calcium hydroxide can enhance the curing process of concrete. When this saturated water is used, it can help maintain a moist environment and contribute to the hydration process of the cement particles, leading to improved strength and durability of the concrete.

Using water that contains calcium hydroxide is particularly beneficial in scenarios where the formation of calcium silicate hydrate is desired, which is critical for the strength development of concrete. Other types of water may not provide the necessary conditions or could introduce contaminants that might negatively affect the performance of the concrete during curing. For instance, river water may carry sediments or impurities, tap water might not have the ideal chemical composition, and filtered rainwater may lack the necessary components present in saturated calcium hydroxide. Therefore, the specific choice of water is crucial for achieving optimal curing of the concrete as outlined in the C511 standard.