5. Conduits

Two very different manufacturing methods are used for the ducts, depending on whether they are of the storey-height type or higher (up to 6 m) or of the manuportable type, often limited to a height of 0.33 m.

When used for ventilation, ducts are often made from standard aggregate concretes. In the case of smoke ducts, concrete made from pozzolan or expanded clay aggregates is often used.

• For floor-level ducts, production is carried out in a horizontal position, using metal molds and cores (figure 27 ). The latter have a draft of around 1% along their length to facilitate extraction from one end.

  Once the reinforcement...