What standard method is commonly used to determine the air content of fresh concrete?

What standard method is commonly used to determine the air content of fresh concrete?

• A. ASTM C38
• B. ASTM C1064
• C. ASTM C39
• D. ASTM C231 (pressure method)

Answer: (D)

Measuring air content in fresh concrete is done most effectively with the pressure method. This standard approach, described in ASTM C231, uses a calibrated air meter to determine the percentage of air voids in the plastic concrete by applying and releasing pressure in a sealed chamber and measuring the resulting change. The calculation, based on the known chamber and sample volumes, gives a direct, quick read on how much air is present, which is crucial for understanding workability, pumping behavior, and durability against freezing and thawing. The other standards listed focus on different properties—compressive strength or temperature measurements—so they don’t provide a method for determining air content.

Measuring air content in fresh concrete is done most effectively with the pressure method. This standard approach, described in ASTM C231, uses a calibrated air meter to determine the percentage of air voids in the plastic concrete by applying and releasing pressure in a sealed chamber and measuring the resulting change. The calculation, based on the known chamber and sample volumes, gives a direct, quick read on how much air is present, which is crucial for understanding workability, pumping behavior, and durability against freezing and thawing. The other standards listed focus on different properties—compressive strength or temperature measurements—so they don’t provide a method for determining air content.