GB1447059A - Stressed hollow concrete pipes - Google Patents

Abstract

1447059 Casting hollow concrete pipes G R HUME 10 Aug 1973 [10 Aug 1972] 38105/73 Heading B5A Hollow concrete pipes are formed by coating a stressable tendon with an antibonding agent, placing at least one coated, reinforcing tendon in a mould concentrically with the mould walls, partitioning the mould cavity longitudinally so as to cast the pipe with a longitudinal split in the concrete thereof with the tendon(s) on both sides thereof, expanding the pipe radially outwardly to stress the tendon(s), the antibonding agent allowing relative circumferential movement between the tendon(s) and cast concrete, and filling the split to form a circumferentially continuous pipe. As shown in Figs. 1, 2, the concrete 10 is cast vertically or moulded horizontally and centrifugally between inner mould section 1 and outer section 2, the tendon 3 being positioned helically therebetween by comb plates 4, and an inner dividing plate 6, which together partition the mould cavity longitudinally. Reinforcing steel (not shown) may also be placed in the cavity. The pipe may be circular or elliptical in section and may have thickened walls (Fig. 4, not shown). The cast pipe is then expanded by bag (20, Fig. 3, not shown) or by an expanding mandrel not further disclosed), the plates 4, 6 removed and the gaps filled, e.g. by cement or epoxy resin or other non- settable materials, e.g. plastics, wood, metals or plastics-coated metals.