Stackable stirrup mat

A concrete pipe having a generally cylindrical welded wire reinforcing cage embedded therein and including a stirrup mat joined to the cage at the crown reinforcing portion thereof and another at the invert reinforcing portion thereof, wherein said mats include a plurality of stirrup projections, each of said stirrup projections being joined to one of a plurality of base wires which in turn are joined to a plurality of tie wires such that the stirrup projections project out of the plane defined by the base wires and tie wires, the improvement in said pipe comprising:

• each of said stirrup projections of said mat including a generally vertically extending leg having a longitudinal axis and a generally laterally extending anchor having a lateral extremity extending towards a vertical plane within which said leg extends, said leg and said anchor being configured so that the lateral extremity of said anchor does not project to any significant degree beyond a vertical plane passing through and extending along the base wire to which the projection is joined, each said projection has a question mark configuration including a bottom portion extending away from said longitudinal axis, an intermediate portion extending generally parallel to said longitudinal axis, and a top of the question mark comprising said laterally extending anchor of said projection, which top portion extends towards said longitudinal axis and said vertical plane, and said question mark opening towards the vertical plane within which said leg extends.