PT TECHNOLOGY (POST TECHNIONING TECHNOLOGY)

Post Tensioning is a cleaver way of reinforcing concrete during construction. In General, Concrete has Compressive strength, i.e bears its own load, however it lacks Tensile Strength. So whenever live load is added , it has possibility of breakage, to mitigate this, Rebar (Reinforcement Bar – Steel Bars) are added to the Concrete to give it Tensile Strength. However, Rebar provides Passive Reinforcement, i.e it takes the load, only when Concrete failed and cracked. It limits the cracks from developing more.

Whereas, to mitigate this, Post Tensioning provides Active reinforcement. PT provides compressive stress on the material, which offset the Tensile Stress that concrete may face due to load. PT is applied by use of post tensioning tendons.

Below are the elements in post tensioning technology:

1. Prestressing Steel Strands (Tensile strength 4 times more than normal bars)
2. Sheathing & Protective ducting (This allows Steel Strands to move when Tensioning force is applied post curing of concrete)
3. Grout / Corrosion Inhibiting coating
4. Anchorages (Locking using anchors)
   
   
   

Advantages of Post Tensioning:

1. Flexibility in designs by column free spaces.
2. Faster Construction
3. Reduced Maintenance cost
4. Potential for increasing loading on the structure
   
   
   

Type of Post Tensioning:

1. Internal Bonded Tendons: In this method, Ducts are grouted, so Tendons are locked.
2. Internal Unbonded Tendons: Ducts are not filled with grout, on Anchors at the edges are grouted.
3. External Unbonded Tendons: Tendons are installed on the outer surface of concrete structures. It allows access for maintenance and refurbishment.
   
   
   

PT tensioning system should be installed by PT Specialist Companies only, who’s team has relevant experience and training to verify the work. PT work can start post completion of shuttering /foam work and laying of bottom reinforcement. Then ducting will be laid, followed by placing strands using strand pushing machine. Then anchors will be placed.  Concrete placement follows next. When Concrete has attained its minimum strength, strands are anchored and stressed with a large multi strand jack or stressing tool. When jack reaches the correct load, it releases the tendons. The duct is then filled with cementitious grout to provide corrosion protection. BBR Post tensioning Technology is widely used and usually they are members of BBR Network.