ACI Concrete Field Testing Technician - Grade I Practice Exam

What is the initial curing temperature range required for concrete mixtures with specified strengths of 6000 psi or greater?

1. 60 to 70 degrees F

2. 68 to 78 degrees F

3. 50 to 60 degrees F

4. 80 to 90 degrees F

The correct answer is: 68 to 78 degrees F

The correct answer indicates that the initial curing temperature range for concrete mixtures with specified strengths of 6000 psi or greater should be between 68 to 78 degrees Fahrenheit. This temperature range is crucial because it helps ensure optimal hydration of the cement. Proper curing temperatures are essential for the development of strength in concrete, as temperatures that are too low can slow the hydration process and potentially lead to incomplete curing, which compromises the concrete's strength and durability. Conversely, temperatures within this specified range promote the chemical reactions that lead to effective bonding of the cement particles and the aggregates, enhancing the overall performance of the concrete. Maintaining this temperature range during curing also helps mitigate the risks of thermal stress and shrinkage cracking that can occur at extreme temperatures. The other temperature options listed fall outside the ideal range and may not facilitate the necessary conditions for strong and durable concrete mixtures. For concrete with high strength specifications like 6000 psi or more, the focus is on ensuring a controlled environment that fosters adequate hydration and minimizes issues related to temperature fluctuations.