Typically, air-entraining admixtures are added to exterior concrete to increase the concrete's durability. When you think of exterior conditions, you think of freezing temperatures. Thus, shouldn't air be added to concrete for a freezer floor slab as well, since the concrete will be exposed to freezing temperatures? Not necessarily.
Foundations and exterior pavements exposed to freezing and moisture are made with air-entrained concrete to protect them from damage caused by freeze/thaw cycles. However, virtually all freezer floor slabs stay at the freezer's operating temperature until the end of the freezer's useful life. Under normal conditions, no moisture or ice is on a freezer floor. Because of this stable environment, with no freeze/thaw cycles, air entrainment is not required.