Concrete kept at a temperature of how many degrees for one day will usually reach the 500 psi compressive strength needed to prevent damage from freezing?

Concrete kept at a temperature of how many degrees for one day will usually reach the 500 psi compressive strength needed to prevent damage from freezing?

• A. 50 degrees
• B. 60 degrees
• C. 70 degrees
• D. 40 degrees

Answer: (A)

Maintaining concrete at about 50°F for the first day is the practical guideline to reach roughly 500 psi of compressive strength. At this temperature, hydration proceeds at a steady rate, allowing the concrete to develop enough strength quickly enough to resist damage if freezing occurs. Temperatures around 60–70°F would also reach 500 psi, and faster, but the question uses 50°F as the typical minimum that will usually achieve that strength in a day. If kept at 40°F, hydration slows significantly and reaching 500 psi in one day becomes unlikely, increasing the risk of freeze-thaw damage.

Maintaining concrete at about 50°F for the first day is the practical guideline to reach roughly 500 psi of compressive strength. At this temperature, hydration proceeds at a steady rate, allowing the concrete to develop enough strength quickly enough to resist damage if freezing occurs. Temperatures around 60–70°F would also reach 500 psi, and faster, but the question uses 50°F as the typical minimum that will usually achieve that strength in a day. If kept at 40°F, hydration slows significantly and reaching 500 psi in one day becomes unlikely, increasing the risk of freeze-thaw damage.