Moulds for precast
Standards precast concrete units are generally formed in steel moulds, that are suitable for multiple, repetitive use. Smaller units may be cast in moulds having multiple compartments (i.e. a number of units are cast at the same time) that are placed on a vibrating table to compact the concrete. Larger moulds (e.g. for bridge beams) may have vibrators built into them. The moulds are often designed so that they can be readily adapted to produce units of different length or, in the case of standard bridge beams, units of different cross-section.
For special applications, or short production runs, wooden moulds are commonly used.