Adding an air-entraining agent to concrete dramatically improves resistance to surface scaling caused by freezing and thawing and deicing agents. But the correct air content must be consistently maintained from batch to batch to provide maximum protection. Hot weather, dirty aggregates, overmixing and a number of other conditions can break down the air void system.
HOW IS AIR CONTENT MEASURED?
There are two standard methods for measuring air content at the jobsite: the pressure method and the volumetric method. Detailed procedures for performing these tests are given in American Society for Testing and Materials (ASTM) publications.
Any contractor who builds parking lots, driveways, patios or sidewalks in northern climates should consider testing air content regularly. The expense of buying and using an air meter is minor when compared with the cost of repairing or replacing frost-damaged concrete.