Air content test
A field measurement of the percentage of air in fresh concrete, used to verify freeze-thaw protection. Performed with a pressure meter or, for porous aggregate, a volumetric meter.
What does air content test mean?
Air content is checked at the point of placement rather than at the plant, because pumping, dropping, and hauling all change it. Too little air leaves the concrete vulnerable to freeze-thaw damage; too much costs compressive strength. The pressure method is standard for ordinary aggregate, while lightweight and porous aggregates require the volumetric method to avoid false readings.
In practice
On winter exterior work this test is often the difference between a slab that survives a decade of salt and one that scales in year two.