Concrete should be placed in 4-foot lifts (passes), at a rate of 8-feet per hour. For an 8-foot wall, concrete is placed in 2 lifts. Approximately 30 minutes after placement, concrete will support its own weight, allowing for the 2nd lift to be placed above it. CAUTION! If concrete slump exceeds 6″ or contains liquefiers, place it in 3-foot lifts, to reduce the risk of a form failure.