Q. Defaults for precast concrete pipes made by spinning?

Small diameter precast concrete pipes are generally manufactured by spinning method. The spinning method fundamentally makes use of the principle of centrifugal forces that diminishes towards the centre of precast pipe. Therefore problems such as presence of voids and variation of dimension take place frequently and remedial works like filling of voids by cement mortar has to be performed depending on the severity of deficiency. 

Large diameter precast concrete pipes are generally produced by vertical casting method. In this method concrete pipes are usually placed upright with spigot staying on top, resting on socket moulds before freshly-placed concrete has set. There is a possibility of deformation of pipe spigots to form oval shapes.