Making Precast , Prestressed, Concrete
  Precast, prestressed concrete lintels are made of high-strength concrete and wires of special steel. Such lintels rely for their effectiveness on the properties of and the interaction between the concrete and the wires.
  The aim of this paragraph is to give a brief guidance on the selection of materials for the proportioning of concrete, steel specifications, principles of manufacture, and sources of design information and prestressing equipment.
  Precast lintels must meet the following requirements:
  They must contain sufficient steel to carry the load once built in.
  They must be as light, and therefore slender, as possible.
  They must not crack easily when lifted or handled.
  It has been found that the last two requirements can be met only if the concrete is prestressed, i.e. the concrete is ‘‘precompressed’’ so that it will not crack easily. Ordinary reinforced concrete does not work for such slender shapes.
The following equipments are needed: Suitable moulds (which may have to be purpose-made). A jacking system incorporating a means of anchoring the wires, jacks that can be closely controlled (for accurately stretching the wires) and a means of gripping the wires.
 
Copyright Information | All Rights Reserved