ASTM C173/C173M
Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
Measuring air content in fresh concrete by displacing the air with water and alcohol, the method used when the aggregate is lightweight or porous.
Who needs it
Testing labs and inspectors working with lightweight concrete, some slag and recycled aggregates, and any mix where the pressure meter is not valid.
What the test involves
A measured sample of fresh concrete is placed in a bowl fitted with a graduated top section, then agitated with water and a small amount of alcohol until the air is driven out of the paste. The drop in liquid level corresponds to the air that was in the concrete. It is more labor-intensive than the pressure method but does not care whether the aggregate itself contains air voids.
Common misconceptions
- It is not a less accurate backup test. On porous aggregate it is the correct method and the pressure meter is the wrong one.
- The alcohol is not an optional additive — it suppresses foam so the reading can be taken, and skipping it distorts the result.
- Getting a different number than a pressure meter on lightweight concrete is expected behavior, not evidence that one operator made a mistake.
Official source
We summarize scope and purpose only. The full text belongs to the issuing body — read it at the official source. ASTM International