What information do you have concerning a flotation technique for pavement construction?
Our best guess is that this is a method which has been used experimentally to reduce sub-grade restraint on slabs. It involves covering the sub-base with a layer of sand, and then placing deflated rubber tubes across the slab. The tubes are covered with building paper, the concrete is placed and allowed to set, and the tubes are then inflated to raise the slab, freeing it from restraints. The tubes are subsequently deflated to lower the slab onto the sub-base. According to a report published in FIP Notes for March/April 1971, this procedure does indeed achieve an immediate reduction of subgrade restraint to quite low levels, but the advantage tends to diminish gradually.