If concrete is kept at a temperature of 50 degrees for one day, what compressive strength is typically reached to prevent damage from freezing?

• A. 200 psi
• B. 500 psi
• C. 700 psi
• D. 900 psi

Answer: (B)

Developing enough early strength to withstand freezing is the idea. When concrete is kept at about 50°F for a day, hydration proceeds, but more slowly, and the one-day compressive strength is typically around 500 psi. That level provides a practical buffer against damage if freez­ing temperatures occur before the mix has fully cured. A strength of about 200 psi would be too low to resist the stresses from freezing, while 700–900 psi would usually require warmer curing or a longer time than just one day at 50°F. So, 500 psi is the typical target for preventing freeze damage under these conditions.