Tension wire for concrete, commonly known as post tension cables or tendons, are steel cables that are used to reinforce concrete. Unlike traditional methods where reinforcement is placed before concrete sets, these cables are tightened after the concrete has been cast and reached sufficient strength.
Understanding Tension Wire in Concrete
In concrete construction, reinforcement is crucial to provide tensile strength, as concrete is strong in compression but weak in tension. While conventional reinforcement like rebar is placed before the concrete is poured, tension wire (post-tension cables) offers a different approach to reinforcing concrete structures.
Here's a breakdown based on the provided reference:
- What it is: Steel cables specifically designed for reinforcing concrete.
- Alternative Names: They are also widely known as post tension cables or tendons.
- Purpose: Used to reinforce concrete, providing the necessary strength to withstand pulling forces (tension) and improve structural performance.
- Key Difference from Rebar: The primary distinction lies in the timing of applying tension. Traditional rebar is passive reinforcement embedded before concrete hardens. Post-tension cables are active reinforcement; they are tensioned (tightened) after the concrete has been cast and has gained sufficient strength.
How Post Tensioning Works
The process of using tension wire (post tension cables) involves placing sheathed or coated steel cables within the concrete formwork before the pour. After the concrete has hardened and achieved the required strength, hydraulic jacks are used to pull the tendons from the ends. This pulling action puts the concrete element under compression, which effectively counteracts the tension that the structure will experience under load. The cables are then anchored in place, locking in the tension.
This technique is particularly useful for creating thinner slabs, longer spans without support columns, and stronger structures that can resist cracking.
