Abstract: Apparatus for manufacturing precast, prestressed, hollow-core, concrete slabs, including an extruder which is movable along a fixed casting bed to extrude from a relatively dry concrete mix a slab having longitudinally extending hollow cores and grout keyways extending along the slab sides. Multiple, core-forming augers in the extruder are shaped and positioned with respect to a feed opening in the extruder in a manner which eliminates cavitations in the slab and provides smooth, well formed slab surfaces and proper bonding between the concrete and prestressing wires.

Abstract: A structural connection between adjacent ends of vertically superimposed precast columns in a structural framework of precast beams and columns. As in precast columns of the prior art sections of tubing are cast in the columns and extend longitudinally of them. However, the tubing at one end of the columns, rather than terminating at or just beyond the column end face, projects outwardly of the column a substantial distance, preferably through an opening formed through a beam at a beam-column intersection where the column joint is formed, and one end of a spindle is received in this portion of tubing and also in a second portion of tubing projecting only a slight distance from the opposite end of the adjacent column. A washer or washers may be loosely attached to or merely slipped over the spindle to engage the opposed ends of the tubing and transfer loads from an upper to a lower column. This construction provides shorter length spindles and a direct transfer of loads from upper to lower columns.

Abstract: In a structural framework which includes precast, concrete columns an improved connector is provided for transferring the load of superimposed columns to those beneath them. The connector consists of a spindle which is received in hollow cores of the columns and a sleeve within and to which the spindle is positioned and connected in any convenient manner, such as by a press fit, plug or spot welds. The sleeve transfers the vertical load from one column to another and incremental washers may be utilized intermediate an upper end of the sleeve and a lower end of a column to adjust the vertical elevation of an upper column.