Here are 10 facts about Unbonded Post Tensioning.
1. One tendon consists of:
- A high-strength steel strand (ASTM-416)
- PT coating (“grease”)
- Plastic sheathing (HDPE)
- Watch our YouTube video about how to make a PT tendon.
2. The high-strength steel strand has 6-wires braided around 1 king-wire (total of 7-wires). The “braiding-action” helps to strengthen the steel, similiar to hair.
3. One strand (270 ksi) has a cross-sectional area of only 0.153 square inches but has a breaking strength of approximately 41,000 lbs. That’s strong enough to hold 6 Ford Explorer without breaking!!! CLICK HERE to find out what your car weighs.
4. The PT coating acts as a corrosion inhibitor to protect the steel from corrosive compounds (water, salt, etc.) It also makes for a good shoe-shine!
5. The high-density-polyethylene plastic sheathing is extruded onto the steel strand and keeps the strand from bonding to the concrete. It’s thickness is only 40 mils to 50 mils. That’s roughly 1.0 to 1.25 millimeter or 0.04 to 0.05 inches.
– Neel Khosa
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