CONCRETE PIPE Reinforcement Fabrication Cage machines, mandrels, and wire rollers are the three most common means of fabricating reinforcing cages in a concrete pipe plant. The cage is an assembled unit of steel reinforcement consisting of circumferential and longitudinal bars or wires. A cage machine uses reels of cold drawn steel wire. By means of adjustable guides, it positions the longitudinal wires while wrapping the circumferential wire in a helix around the longitudinals. Intersections of the circumferential and the longitudinal wires are automatically welded. The process produces a continuous cage. When the desired cage length has been reached, the longitudinals and circumferentials are cut with shears. In using mandrels to fabricate cages, the mandrel is adjusted to the required diameter. The longitudinal steel is placed on the mandrel, and the circumferential steel is helically wrapped around the turning mandrel. The intersections of the longitudinals and the circumferentials are automatically welded. Wire rollers use welded wire fabric in rolls or flat mats with the desired size and spacing of longitudinal and circumferential wires. When the proper length of fabric has been formed by the roller, it is cut and spot welded to form the cage. Four cage configurations are in common use: single circular cage, double circular cage, single elliptical cage, and a combination of an elliptical cage and one or more circular cages (pg 16). Additionally, quadrant reinforcement can be used to provide increased steel areas in the tensile zones of the pipe. Quadrant reinforcement can be provided by overlapping cages and incorporating mats. Steel area is a commonly used term for describing the reinforcement in concrete pipe. When the term is used, it refers to the square inches of circumferential steel per linear foot; that is, if a section of pipe were to be cut lengthwise, the steel area is the sum of the cross-sectional areas of the exposed circumferential wires in one linear foot of pipe. PAGE 18 LAFARGE PIPE eMANUAL