15.20mm Unbonded Low-Relaxation Prestressing Steel Strand – High-Performance Solution for Modern Infrastructure
Engineered for durability, efficiency, and long-term structural integrity, the 15.20mm unbonded low-relaxation prestressing steel strand is a premium-grade solution widely adopted in global construction projects. This high-tensile steel product combines advanced material science with proven engineering practices to deliver superior performance across large-span buildings, bridges, geotechnical systems, and specialized industrial structures. Designed to minimize stress loss while maximizing load-bearing capacity, it represents a significant advancement over traditional bonded prestressed systems.
Key Features & Technical Advantages
Manufactured from seven ultra-high-strength steel wires, this 15.20mm diameter strand offers a nominal cross-sectional area of approximately 140 mm² and a minimum tensile strength of 1860 MPa—ideal for demanding civil engineering applications. The unique "unbonded" design features a corrosion-inhibiting grease layer (≥50g/m) encapsulated within a high-density polyethylene (HDPE) sheath, creating a fully sealed barrier that allows free movement under tension without bonding to concrete. This isolation ensures minimal frictional losses during installation and exceptional resistance to environmental degradation. Furthermore, through controlled super-tensioning and heat treatment processes, the strand achieves a stress relaxation rate of no more than 2.5% after 1000 hours at 70% of its standard tensile strength—an improvement of over 60% compared to conventional strands.
With an elongation of at least 3.5% and a yield strength coefficient of 0.93, the strand meets stringent requirements for ductility and energy absorption in dynamic loading conditions. Its HDPE sheath provides excellent resistance to ultraviolet radiation, acidic environments, and alkaline exposure, ensuring a service life exceeding 50 years even in aggressive climates. These properties make it particularly suitable for marine environments, seismic zones, and regions with extreme temperature fluctuations.
Applications Across Global Infrastructure Projects
This prestressing system excels in scenarios where weight reduction, rapid construction, and long-term maintenance-free operation are critical. In commercial and residential high-rise developments, it enables thinner floor slabs—reducing concrete usage by up to 15%—while maintaining structural safety for spans between 8–12 meters. For bridge engineers, the absence of grouting simplifies external cable installation, shortening project timelines by up to 30 days. Geotechnical applications benefit from consistent anchoring force retention; real-world monitoring data from slope stabilization projects shows less than 3% stress decay over one year. Additionally, nuclear containment structures and LNG storage tanks utilize this strand in circumferential prestressing systems to resist internal pressure and prevent crack-induced leakage—highlighting its role in critical infrastructure resilience.
User Feedback and Industry Validation
Global contractors and structural designers have consistently praised the reliability of 15.20mm unbonded low-relaxation strands in complex projects. Engineers report reduced labor costs due to simplified tensioning procedures and fewer quality control checks. Maintenance teams appreciate the lack of need for periodic inspection or re-grouting, especially in hard-to-access locations such as elevated highways or underground parking facilities. Case studies from Europe, North America, and Southeast Asia demonstrate improved lifecycle cost efficiency, making this strand a preferred choice for sustainable and future-ready construction.
Frequently Asked Questions
What makes unbonded prestressing different from bonded systems? Unlike traditional methods that rely on grouted ducts to bond steel to concrete, unbonded strands remain isolated, allowing independent deformation and reducing frictional losses during tensioning. This results in higher effective prestress and easier repair or replacement if needed.
Is it suitable for harsh climates? Yes, thanks to its HDPE sheathing and anti-corrosive lubricant, the strand performs reliably in coastal areas, cold regions, and urban environments with high pollution levels.
How does it contribute to green building standards? With lower embodied energy per unit length and extended lifespan, it supports LEED and BREEAM certification goals. New eco-friendly variants using bio-based greases and biodegradable polymers are now emerging to further reduce environmental impact.
Can it be integrated into smart infrastructure? Absolutely. Some modern installations embed fiber-optic sensors inside the sheath to monitor stress distribution and detect early signs of damage—enabling predictive maintenance and digital asset management.
Why choose 15.20mm specifically? This size strikes an optimal balance between strength, handling ease, and compatibility with standard anchorages and tensioning equipment, making it ideal for both new builds and retrofitting existing structures.
Manufactured by Chunpeng Group—a globally recognized leader in prestressed concrete materials with over three decades of expertise—the 15.20mm unbonded low-relaxation strand sets the benchmark for innovation, quality, and sustainability in structural engineering worldwide.
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