Concrete pipes for various industrial purposes, including water supply, drainage, sewerage and irrigation, and for lamp standards, septic tanks and well linings, and the following articles composed wholly or mainly of concrete, anchor blocks, box culverts, crib blocks for fences or retaining walls, fence posts, grease traps, guttering, incinerators, kerbing, manhole units, paving slabs, sewerage fittings, silo staves, water stave tanks, pretensioned beams and postensioned beams.