Q.: Please give your recommendations for placing and vibrating architectural concrete in a 14-foot-high wall to be cast in a single placement. We are concerned about our ability to vibrate effectively enough to get a surface that is the same from bottom to top.
A.: A method that is reported to be effective is to provide access doors at several levels in the back face, which will not be exposed to view. These doors serve two purposes. They are entries through which concrete can be placed without dropping it long distances and they are ports through which vibrators can be inserted and operated. Concrete is placed in small batches as near as possible to its final location. Normal good vibrator practice is used to consolidate the concrete as uniformly as possible. The openings at each level are closed as soon as they are no longer needed and the openings are promptly sealed against leakage. The back face will be marred by the outlines of the openings, but presumably that face will not be visible.