All concrete that will be subject to freezing when moist or be exposed to deicing salts should contain which admixture?

All concrete that will be subject to freezing when moist or be exposed to deicing salts should contain which admixture?

• A. Water-reducing agent
• B. Air-entraining agent
• C. Accelerator
• D. Retarder

Answer: (B)

The key idea is protecting concrete from freeze–thaw damage when moisture is present or when deicing salts are used. An air-entraining admixture creates a network of tiny, well-distributed air voids within the cement paste. These micro air voids act as tiny pressure-relief chambers when water inside the pores freezes and expands. By giving ice something to occupy without building up pressure, the concrete resists cracking, spalling, and other freeze-thaw–related deterioration. This same air void system also helps reduce surface scaling and damage when salts are present, since the expanded ice and salt solution have somewhere to go without causing as much internal stress. Water-reducing agents change the workability and water-cement ratio but don’t add the necessary air void system, so they don’t provide the same freeze-thaw protection. Accelerators and retarders modify curing time rather than the pore structure that relieves freezing pressure, so they don’t enhance freeze-thaw durability in the same way.

The key idea is protecting concrete from freeze–thaw damage when moisture is present or when deicing salts are used. An air-entraining admixture creates a network of tiny, well-distributed air voids within the cement paste. These micro air voids act as tiny pressure-relief chambers when water inside the pores freezes and expands. By giving ice something to occupy without building up pressure, the concrete resists cracking, spalling, and other freeze-thaw–related deterioration. This same air void system also helps reduce surface scaling and damage when salts are present, since the expanded ice and salt solution have somewhere to go without causing as much internal stress.

Water-reducing agents change the workability and water-cement ratio but don’t add the necessary air void system, so they don’t provide the same freeze-thaw protection. Accelerators and retarders modify curing time rather than the pore structure that relieves freezing pressure, so they don’t enhance freeze-thaw durability in the same way.