When is the optimal time to place concrete regarding water addition?

The optimal time to place concrete regarding water addition is within 90 minutes of adding water at the concrete plant. This timeframe is crucial because concrete's workability and strength are significantly affected by the mixing process and the hydration of the cement. Once water is added to the dry ingredients, hydration begins, and if placement is delayed beyond this 90-minute window, the risk of poor workability, increased risk of setting before placement, and compromised strength can arise.

Concrete must be placed as soon as possible after mixing to ensure that it achieves the intended mechanical properties. After about 90 minutes, the concrete can start to set, especially in warm weather, making it more challenging to effectively place and finish the material. Additionally, the industry standard emphasizes that concrete should be transported and placed swiftly to manage the effects of temperature and time on the setting process.

While the other choices may contain relevant information about water addition or placement, they do not encapsulate the critical time factor regarding concrete placement after water has been added. This makes the timeframe of 90 minutes the optimal recommendation for ensuring high-quality results in concrete placement.