Prefabrication concrete building elements contg. cavities - made using extruder where compaction zone and mould walls are vibrated

摘要

Extruder for moulding prefabricated concrete building elements, has a concrete mix passing through a loading funnel and at least one screw feeder to a moulding station provided with at least one mandrel for making a cavity in the element. Between the screw feeder(s) and the moulding station a compaction zone; the axes of the screw feeder and mandrel are displaced wrt. each other, both rotating independently; the screw feeder is driven to compact the mixt and press it into the moulding station; and the mould walls are vibrated at above 22,000 oscillations/minute to reduce friction between the mould walls and the mix. The mandrel(s) may also be oscillated. The cavities in the mouldings do not require to be round and very low oscillation amplitudes are employed; several cavities can be produced simultaneously.