Q.: Would an impact hammer be useful for preventing air pockets?

A.: One contractor did this successfully to eliminate surface holes varying in size from those commonly called bugholes up to those 1 inch in diameter. He used an impact hammer to which he fitted a 2 1/2-inch-diameter button head. The hammer was used against the rails and walers. The low frequency of the impact hammer was reported to be more effective than an external form vibrator. The inner faces of the forms on the job were plastic-overlaid plywood.

Besides vibrating the forms, the contractor is well advised to avoid sticky mixes, especially those containing a large amount of fine aggregate passing the Numbers 30, 50 and 100 sieves.