What Functions of Unbonded PC Steel Strand Three Components？

Unbonded PC Steel Strand is a critical material in post-tensioned prestressed concrete structures, widely used in bridges, high-rise buildings, foundation pit support, long-span structures and other engineering projects. It consists of three components: steel strand, anti-corrosion grease and HDPE plastic sheath. The three components work together to ensure that the prestressing tendon performs stably and safely in concrete over the long term.

As a professional manufacturer and supplier of unbonded PC steel strands, we implement strict quality control over each structural layer. Our products fully comply with international standard JG161-2004. Steel is in accordance with GB/T5224-2014, or EN10138/BS5896, or ASTM A416, or other standards clients require. Sheathing: GB11116, GB/T9341. Grease: JG3007-1993. We can supply products meeting your requirements and provide professional technical support. The specific functions of each component are as follows:  

1. PC Steel Strand

PC Steel strand is the core load-bearing component of unbonded steel strand, bearing the full prestressing tension.

Functions:

Withstand tension and provide prestress.

- Load transfer: Elastic retraction force is generated during tensioning, transferring pressure to concrete members via anchors, thus improving crack resistance and rigidity of members.

- High strength: Normally twisted from multiple (e.g. 7) high-carbon steel wires, featuring extremely high tensile strength and good flexibility for easy transportation and construction.

Our Advantages:

- Made of high-quality high-carbon steel wire rods, stabilized for high strength and low relaxation.

- Manufactured strictly in line with GB/T 5224, ASTM A416 and other standards.

- Each batch passes multiple tests including tensile strength, elongation and relaxation.

- Stable tensioning performance, significantly improving the safety and durability of engineering structures.  

2. Anti-Corrosion Grease

Anti-corrosion grease is filled between the steel strand and the sheath, acting as a lubricating and anti-corrosion layer, and the core layer for achieving the unbonded effect.

Functions:

Anti-corrosion & anti-rust, lubrication & friction reduction, isolation & protection.

- Anti-corrosion & anti-rust: Grease fully coats the steel strand, isolating air and moisture to prevent rust — key to the durability of unbonded tendons.

- Friction reduction & lubrication (key to unbonded effect): Provides an extremely low friction coefficient. During tensioning, the steel strand can slide freely inside the sheath, ensuring uniform distribution of tension and minimal tension friction loss.

- Stress relief: Under extreme high temperatures such as fires, the grease melts and flows out, preventing excessive additional pressure on concrete caused by thermal expansion of the steel strand (buffering effect).

Our Advantages:

- High-performance anti-corrosion grease with excellent high and low temperature resistance.

- Resistant to leakage and cracking, maintaining stable performance long-term.

- Low friction coefficient for smoother tensioning, improving construction efficiency and reducing equipment wear.

- Greatly enhances durability of prestressing tendons and lowers long-term maintenance costs.  

3. HDPE Plastic Sheath

The HDPE plastic sheath serving as the physical barrier wrapped on the outermost layer.

Functions:

Physical isolation, mechanical protection, preventing grease leakage.

- Mechanical protection: Protects internal steel strand and grease from external mechanical damage (e.g. impact by vibrators during concrete pouring or puncture by sharp aggregates).

- Waterproof & anti-seepage: Acts as a robust physical barrier, preventing ingress of external moisture, cement slurry or other corrosive media.

- Form a non-adhesive interface: Completely separates the steel strand from surrounding concrete, avoiding adhesion under deformation and enabling longitudinal sliding of the steel strand inside concrete.

Our Advantages:

- Extruded from brand-new HDPE material with uniform wall thickness and smooth surface.  

- High impact and puncture resistance for safer construction.

- Excellent sealing, waterproofing and anti-seepage performance.

- Effectively extends service life of prestressing tendons and reduces engineering maintenance costs. 

Summary

The PC steel strand provides stable and reliable prestress; the grease ensures tension performance and durability; the HDPE sheath offers a physical protective barrier. This structure eliminates the need for duct reservation and grouting during construction, greatly simplifying procedures while avoiding corrosion risks caused by incomplete grouting. It is an ideal solution for modern prestressed engineering. Whether your project involves bridges, subways, high-rise buildings or special engineering, we can provide qualified unbonded PC steel strands and one-stop solutions. Welcome inquiry and contact us via the email and telephone on our official website.