Housing in Southern Africa November 2015

technology plant

requirements, low unit production cost was a critical objective for Perse directors. This requirement was met by using the weiler extruder (MAX- truder) for slab/panel production. The extruder uses a dual vibration compaction system to compact a dry concrete mix with low cement con- tent (water cement ratio 0.32 approx.) and no admixtures, which results in elevated final compressive strengths averaging 75 MPa (750 kg/cm²). Higher strengths allow for lighter and stronger elements, a key feature of weiler slab and panel precast ele- ments. Combining lower concrete costs with lighter (lower concrete volumes) sections, means weiler extruded slabs/panels cost 28% - 40% less per m² than wet-cast slabs/ panels. For the new factory layout, weiler design engineers were faced with challenges: • Integration of the new factory alongside an existing production hall and systems without disrup- tions to processes • Designing-in work and material flows to separate the rawmaterial storage andmixing areas, from fin- ishedproduct, storage and loading areas • Providing timely, mixed concrete delivery to precast production up

and flying shuttle system – all fully automated – as well as a hot water heating system for accelerated curing of the products. Even the cranes were part of this extensive order and were shipped from Europe. Following a study of Perse’s re- quirements, the necessary technical equipment was specified for a new hollow core slab plant to be placed beside the existing hall. Included in the offer was a detailed investment analysis that showed that a new weiler production system, using a similar area and material inputs as thewet-cast hall, could produce three times the volumes, with a direct cost saving of 28-40% per m² of precast production. Production cycle times could be reduced to 6 - 8 hours total per bed; one hour to extrude slabs and 5 - 7 hours to cure, cut and lift sections. With four production beds, each 120 metres long, the beds can pro- duce twice a day, so that the daily nominal capacity would be 1 680 m² of flooring or walls, compared with the existing wet-casting system producing 560 m² with eight produc- tion beds. By adding four additional production beds to the new weiler productionhall, nominal capacity can be increased to 3 360 m² of floors or walls per 24 hour period. Following quality and volume

to 200metres fromthe batchmixer station • Ensuring that future expansions, new production additions would be easy and be served by the same infrastructure A critical part of the layout challenge was resolved with the use of an au- tomated batch mixer station placed in the existing material storage and mixing area, delivering concrete by flying shuttle on elevated rails, in- cluding curved sections, to the new hall production area. weiler considers this new ad- vanced extruder factory an important milestone for Perse and is proud to have been the chosen supplier. For add i t i ona l i n format i on email: info@weiler.net or visit www.weiler.net ■

November 2015