A 1994 study examined the effects of concrete handling methods on normal air-entrained concrete. Concrete for a large parking lot and driveway project was placed by pump, crane and bucket, truck-mounted conveyer, and directly from the chutes of ready mix trucks. The primary goal of the test program was to determine how air content, air-void system parameters, and freeze-thaw durability of air-entrained concrete are influenced by placement and consolidation methods.
The concrete mixture used for the tests was a Minnesota DOT mix typically used in local projects. Handling the concrete after discharge unquestionably affected the total air content. However, the results of freeze-thaw testing demonstrate adequate frost resistance despite air loss in the concrete. For this particular concrete mix, the various handling effects did not reduce the freeze-thaw durability of the concrete. In addition, the impact of the handling, particularly pumping, varied from truck to truck (eight truckloads were used). Based on results of testing at the truck chute, it becomes clear that the truck-to-truck variation in air content is generally greater than the variation due to handling concrete from the same truck.