What Is Unbonded Post Tensioning System

An unbonded post-tensioning system is a method of reinforcing concrete structures using high-strength steel tendons that are grouted or filled with grease and covered in a plastic sheath before being tensioned.

Unlike bonded post-tensioning, where the tendons are bonded to the concrete with grout, in an unbonded system, the tendons are free to move within the sheath and are not bonded to the concrete.This allows for more flexibility and easier maintenance as the tendons can be replaced if necessary without affecting the structural integrity of the concrete.

Unbonded post-tensioning systems are commonly used in large concrete structures such as bridges, parking garages, and buildings.

Unbonded Post-Tensioning typically consists of single (mono) strands or threaded bars that remain unbonded to the surrounding concrete giving them the freedom to move locally relative to the structural member. 

The strands in unbonded mono strand systems are coated with specially formulated grease, with an outer layer of seamless plastic extruded in one continuous operation to protect against corrosion. It is e typically used in new construction for elevated slabs, slabs-on-grade, beams and transfer girders, joists, shear walls and mat foundations. Light and flexible, unbonded mono strand can be easily and rapidly installed – providing an economical solution.