For concrete mixtures with specified strengths of 6000 psi or greater, what is the required initial curing temperature range?

For concrete mixtures with specified strengths of 6000 psi or greater, the required initial curing temperature range is critical for achieving the desired properties and strength of the concrete. The optimal initial curing temperature range is determined to ensure that the hydration process occurs effectively, which is necessary for developing the concrete’s strength and durability.

The selection of 68 to 78 degrees Fahrenheit aligns with the industry standards and practices, specifically those outlined by ASTM C 31 and C 9, which highlight the importance of maintaining proper temperature conditions during curing. This temperature range helps to optimize the rate of hydration, ensuring that the cement can effectively bond with the aggregates and develop the required compressive strength.

Lower temperatures can slow down the curing process, which may hinder strength development, while excessively high temperatures can lead to rapid evaporation of moisture and potentially cause issues such as cracking. Therefore, maintaining an initial curing temperature within this specified range is essential for high-strength concrete mixtures to achieve their performance criteria.

The other provided options fall outside the range recommended for high-strength concrete, either being too low or too high, which could adversely affect the hydration process and the overall performance of the concrete.