In cold weather concreting, what is one purpose of air-entrainment?

• A. Improve surface finish
• B. Increase early strength
• C. Prevent freeze-thaw damage through air-entrainment
• D. Decrease set time

Answer: (C)

Air-entrainment adds tiny, well-distributed air voids in the hardened concrete, which provide space for water to expand when it freezes. This relief space reduces internal pressures during freeze-thaw cycles, preventing cracking and deterioration in cold, saturated conditions. That durability benefit is the main purpose in cold weather concreting. The other effects—like surface finish, early strength, or accelerated set time—are not the primary goals of air-entrainment; in fact, air voids can slightly reduce strength and do not speed up setting, and finishing can be more challenging if air content is too high.