Which factors could cause low air content in field concrete, and how should it be addressed?

• A. Under-dosed air-entraining agent, improper mixing, or temperature effects; inspect, adjust mix, remix if needed, and retest.
• B. Over-dosed air-entraining agent and prolonged curing; ignore.
• C. High aggregate content; increase water only.
• D. Using cold water in winter; do nothing.

Answer: (A)

Low air content in field concrete undermines frost resistance and long-term durability, so the test focuses on identifying why the mix isn’t forming the expected air voids. The most common factors are not enough air-entraining agent added, mixing problems that prevent proper dispersion of that agent, and temperature effects that can reduce the effectiveness or stability of the entrained air. The best way to address this is to check the batch against the specification, adjust the dosage of the air-entraining agent if needed, remix the concrete to ensure the air-entraining agent is evenly distributed, and then retest the air content to confirm it meets the target. This approach directly targets the causes and verifies the fix before placement.