DIFFERENCE BETWEEN PRETENSION AND POST TENSION IN CONCRETE
1) Pre tensioning is cheaper because the cost of Sheathing is not involved in it, whereas post-tensioning is costlier because of use of sheathing.
2) Pre tensioning is more durable and reliable but in case of post-tensioning, the durability depends on the ‘Anchorage Mechanism‘
3) Because of small and easy to transport of structural elements, the pre-tensioning is preferred and most popular as compared to post-tensioning.
4) Pre tensioning is more suitable for precast construction works because it is done in factories while post-tensioning can be done in factories as well as on the site
5) Process of casting is different for pre-tensioning and post-tensioning concrete :
The strands are tension before the casting the concrete and in concrete is cast enclosing the tension cables in pretension concrete, but in the case of post-tension concrete, plants are enclosed within a duct in the form, and then concrete is casted
6) In the case of pretension concrete, small sections are to be constructed while in post-tensioned concrete, the size of the member is not limited. Generally long-span bridges are constructed by post tensions
7) Products are changed according to the structure in case of post-tensioned concrete, but similar structures are prepared in pre-tensioning concrete
8) Loss of prestressing is not more (it is about 15%) in post-tensioned concrete, and loss of prestressing is not less (it’s about 18%) in the case of Pre tensioning concrete
9) Mould is used to produce pre-tensioning members in prestressing concrete, whereas cables are used in place of wires, and jacks are used for stretching purposes .
10) In the case of prestressed concrete, the concrete is prestressed with tendons before its placing in position; Whereas in post-tensioning concrete, prestressing is done after the concrete attains sufficient strength.
11) The pre-tensioning method is developed due to the bonding between the concrete and steel tendons, whereas the post-tensioning concrete method is developed to bearing.