Abstract: A machine for "dry mix" packerhead concrete pipe manufacture has two stations and a separable tubular jacket movable therebetween. A rotatable cylindrical packerhead is movable axially within the jacket and a "dry mix" delivery means deposits mix atop the packerhead as it rotates and moves vertically upwardly within the jacket. The packerhead distributes the mix thereabout to form a concrete pipe in the jacket. A radially expandable and contractable core is movable axially in a contracted condition to a position within the pipe and is then expanded. Vibrators within the core are operated to "redensify" the pipe; that is, to compact the mass thereof, to eliminate voids, and to relieve residual forming stresses therein. A guide ring is employed to align the contracted core axially with the pipe during entry and further guiding and supporting devices for the core are provided. Core entry and withdrawal is power actuated as is core expansion and contraction within the pipe.

Abstract: Precast concrete structural units and composite wall structure comprising a plurality of the units stacked vertically in horizontal rows. Each unit comprises a pair of laterally spaced longitudinally extending side panels. A pair of laterally extending connecting arms are connected to or formed integrally with the panels at their respective inner surfaces whereby to secure the panels in relatively fixed position. A mortise-tendon connection between superposed units is provided with a vertically recessed mortise at the bottom of each connecting arm and a complementary vertically projecting tendon at the top of each arm. Each mortise and tendon defines a pair of laterally spaced oppositely facing generally vertical bearing surfaces and each mortise and tendon is approximately 1/3 the total width of the associated structural unit. Longitudinal spacing of connecting arms from each other is approximately twice the longitudinal spacing of each arm from the adjacent end of the side panels.