Composite Materials

What is the difference between pre-tensioning and post tensioning in precast construction?

Pre-Tensioning

Pre-tensioning is done in the factories thus suitable for precast construction works.

In this type of concrete, the pre-stressing cables called the strands are tensioned before casting the concrete and then concrete is cast enclosing the tensioned cables.

Small sections are to be constructed.

Pre-tensioning members are produced in a mould.

The concrete is prestressed with tendons before it is placing in position.

Pre-tensioning is preferred when the structural element is small and easy to transport.

Post-Tensioning

Post-tensioning can be done in factories as well as on the site.

In this type of concrete, the strands are enclosed within a duct in the form and then concrete is cast. The process of tensioning the strands is carried out after the concrete attains its sufficient strength.

The size of a member is not restricted, long-span bridges are constructed by post-tensioning.

Cables are used in place of wires and jacks are used for stretching.

Prestressing is done after the concrete attains sufficient strength.

Post-tensioning is preferred when the structural element is heavy.