15.2mm unbonded PC Strand

Name: 15.70 PC STRAND
Uploaded: 2025-06-17T07:28:18+08:00
Description: 15.20 A brief introduction and application of unbonded low-relaxation prestressing I. Basic concepts and technical

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Payment Type:	T/T
Incoterm:	FOB,CFR,CIF
Transportation:	Ocean
Port:	Tianjin Xingang

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Product Description

Product Attributes

Packaging & Delivery

Product Description

Product Attributes

Brand: Chunpeng

Standard: Aisi, Astm, Bs, Jis

Place Of Origin: China

Application: Construction

Whether Alloy: Non-Alloy

Packaging & Delivery

Selling Units	:	Ton
Package Type	:	The roll is wrapped in three layers of waterproof packaging, the roll eyes are facing up and two fumigated sleepers are tied to the bottom with steel belts.
Picture Example	:

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Product Description

15.20 A brief introduction and application of unbonded low-relaxation prestressing

I. Basic concepts and technical characteristics

Analysis of core parameters

15.20: The nominal diameter of the Prestressed Steel strand is 15.20mm, usually made of 7 high-strength steel wires, with a cross-sectional area of about 140mm². It is one of the most commonly used large-size steel strands in construction projects.

Unbonded: The surface of the steel strand is coated with special anti-corrosion lubricating grease (dosage ≥50g/m), and wrapped with a high-density polyethylene (HDPE) sheath to form a "fully enclosed" isolation layer, so that there is no bonding between the steel strand and the concrete, and it can slide freely when subjected to force.

Low relaxation: The super-tensioning process (generally tensioned to 70%~80% of the standard tensile strength) and heat treatment technology are adopted to make the steel strand 1000 hours stress relaxation rate ≤2.5% (the relaxation rate of ordinary steel strand is about 8%) under the conditions of 20℃ and initial stress 70% standard strength, which greatly reduces long-term stress loss.

Material performance advantages

Mechanical properties: tensile strength standard value ≥1860MPa, elongation ≥3.5%, yield strength coefficient 0.93, meeting the high bearing capacity requirements of large-span structures.

Anti-corrosion properties: HDPE sheath has strong weather resistance (anti-ultraviolet aging, acid and alkali resistance), and the grease layer has both lubrication and anti-rust functions, with a service life of more than 50 years.

2. Typical application scenarios and engineering cases

Application fields Technical advantages Examples

Large-span civil buildings Reduce the weight and thickness of the floor slab (e.g. 15.20 steel strands are used for 8~12m span beamless floor slabs, and the slab thickness can be reduced to 200~250mm) The underground garage of a commercial complex in Beijing uses unbonded prestressed floor slabs with a single span of 10.8m, saving 15% of concrete

Bridge engineering The external cable construction is convenient and easy to maintain later; the internal cable reduces the pipeline grouting process The external prestressed strands of a certain city viaduct use 15.20 unbonded steel strands, and the single-beam tension force reaches 2500kN, shortening the construction period by 30 days

Geotechnical anchoring engineering Adapt to complex geological conditions, small stress loss, and long-lasting and stable anchoring force A slope support project uses 15.20 unbonded anchor cables with a length of 30m and a designed anchoring force of 1500kN. Monitoring data shows 1 After the year, the stress decay is less than 3%.

Special structures are used for structures with extremely high durability requirements such as liquid storage tanks and nuclear power plant containment. The circumferential prestressing system of a certain LNG storage tank adopts 15.20 unbonded steel strands to resist the internal pressure load while avoiding the risk of leakage caused by concrete cracks.

III. Key points and specification requirements of construction

Laying and tensioning

During laying, it is necessary to position according to the design curve (deviation ≤10mm/m), and the spacing between fixed points is ≤600mm to avoid damage to the sheath.

The tensioning sequence follows the principle of "symmetry and batching". The tensioning control stress σcon=0.75~0.80fptk (fptk is the standard value of tensile strength), and the load is held for 5 minutes to eliminate elastic compression loss.

Node processing

A hole mold or groove needs to be set at the anchor end. After tensioning, the excess steel strands are cut off (the length is ≥30mm), and sealed with anchor concrete (strength ≥C30) to prevent rainwater from seeping in.

Standards based on

Chinese standards: "Code for Design of Concrete Structures" (GB 50010), "Technical Code for Unbonded Prestressed Concrete Structures" (JGJ 92).

IV. Comparison with traditional prestressing technology

Comparison dimension 15.20 Unbonded low-relaxation prestress Bonded prestress (such as pre-buried corrugated pipe)

Construction efficiency No need for grouting, fewer processes, and 40%~60% shorter construction period Pre-buried pipes, bundles, and grouting are required, and the process is complicated

Stress loss Low relaxation characteristics make the 10-year loss rate ≤5% Relaxation, friction, and anchoring losses total about 15%~20%

Maintenance cost Fully enclosed anti-corrosion, no need for maintenance in the later period Undense grouting can easily lead to rust of steel strands, making maintenance difficult

Applicable scenarios Structures with large spans, high durability, and difficult maintenance in the later period Structures with small and medium spans and conventional durability requirements

V. Development trends and innovative applications

Intelligent monitoring integration: Some projects pre-buried optical fiber sensors in HDPE sheaths to monitor stress changes and sheath integrity in real time, and realize digital operation and maintenance of prestressed structures.

Green building material upgrade: New bio-based lubricants and degradable sheath materials are being developed to reduce environmental impact and adapt to green building standards.

Chunpeng Group is a leading and professional manufacturer of prestressed concrete (PC) steel materials, with over 30 years of industry experience.

We are committed to delivering high-quality products and innovative solutions for infrastructure and construction projects worldwide.

Our Core Products are pc steel strand (Ultra High Tensile Strength PC Strand, Normal Tensile Strength PC Strand), Unbonded PC Strand, Galvanized PC Steel Strand, Weather-Resistant & Anti-Corrosion PC Strand , and PC Steel Wire.

In addition to our PC strand products, we also supply Prestressed Anchorage Systems and Photovoltaic Mounting Systems.