Correct Answer - Option 1 : post-tensioning
Explanation:
Post-tensioning is a technique for reinforcing concrete. Post-tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. Afterward, once the concrete has gained strength but before the service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges of the concrete.
Post-tensioning is a form of prestressing. Prestressing simply means that the steel is stressed (pulled or tensioned) before the concrete has to support the service loads. Most precast, prestressed concrete is actually pre-tensioned-the steel is pulled before the concrete is poured.
∴ A method of prestressing concrete by tensioning the tendons against hardened concrete is known as post-tensioning.
Pre-tensioning: In this method, the concrete is pre stressed with tendons before it is placing in position. This method is developed due to bonding between the concrete and steel tendons. Pre tensioning is preferred when the structural element is small and easy to transport.
Partial prestressing is basically a prestressed concrete in which prestressed reinforcement and non prestressed reinforcement is used such that tension and cracking in concrete is allowed under service loads.
