For determination of air content in plastic concrete, we normally use ASTM C231 as test procedure. If you have light weight aggregates, you may have to use ASTM C173 test procedure.
Air content is very important for durability in freeze-thaw environments. Specs are commonly location and job specific. We commonly see air (where required) as low as 4% and as high as 8%. ACI, CSA, AASHTO,and other authorities etc. will provide guidance as to suggested air content ranges for various applications.