This test method covers laboratory determination of the air content of hardened portland cement concrete with the use of the high-pressure air meter. This determination is made from the observation of change in linear piston movement with a specimen in the test chamber from that of the linear piston movement with no specimen in the test chamber. This change is due to a replacement of specific volume of compressible air by a specific volume of incompressible water. This standard was formerly designated as provisional standard TP 59.