How to Extend the Service Life of Unbonded Steel Strand?

Unbonded steel strand serves as a core load-bearing component in bridges, high-rise buildings, and water conservancy projects. Its service life is directly linked to the structural safety and operational costs of these structures. Many projects suffer from premature corrosion and performance degradation due to improper initial selection, substandard construction, or inadequate ongoing maintenance. This not only increases repair costs but also poses safety risks. Drawing on our over ten years of experience in prestressed steel strand production and service, we believe extending the service life of unbonded steel strand requires a comprehensive approach throughout the entire lifecycle of procurement, construction, and operation and maintenance. The key approaches can be addressed from the following four perspectives:

1. Avoid Damage to the Anti-corrosion System during Construction

- Prevent rust from forming on the base material during transportation and storage. Our factory uses specialized brackets or protective covers to protect the HDPE sheath from scratches or punctures by sharp objects such as rebar and tools. When storing outdoors, cover with a sunshade or rainproof cloth to prevent UV rays from accelerating sheath aging and rainwater infiltration. If stored for more than three months, we regularly inspect the sheath for damage and rust on the strands, addressing any issues promptly.

- Avoid dragging the strands during installation. Control the force during tensioning to prevent excessive friction that may cause sheath wear or grease loss. After installation, apply sealant promptly and inspect the sheath for integrity. Any damage should be repaired or replaced immediately with specialized anti-corrosion tape. Our factory's unbonded strands can be customized to individual lengths based on project requirements, eliminating the need for additional on-site joints, which can easily become corrosion vents and increase the risk of rust. We also mark the lengths on the outside of the sheath for ease of use during construction.

2. Strengthen Protection in Special Environments

- For chloride-rich areas such as coastal areas and saline-alkali lands, a reinforced product combining a thickened HDPE jacket (≥1.2mm) and salt-spray-resistant anti-corrosion grease is preferred. Rust inhibitors should also be added to the concrete for double protection against chloride ion corrosion. We can provide customized products combining a thickened jacket and highly weather-resistant grease. For large-span projects, we offer precision cutting to reduce on-site joints.

- In high-humidity or high-temperature environments, ensure that the anti-corrosion grease has a dropping point of ≥120°C (no loss at high temperatures) and does not harden at low temperatures to prevent temperature fluctuations from damaging the seal. Install waterproof sealing covers on exposed tensioning ends to prevent moisture intrusion. Our anti-corrosion grease, with a dropping point of ≥150°C and high- and low-temperature resistance (no hardening or loss from -30°C to 80°C), ensures a continuous seal year-round.

3. Selecting Compliant Raw Materials

- We strictly adhere to GB/T 21835 standards to ensure that the steel strand base material strength, HDPE sheath thickness (≥1.0mm), and anti-corrosion grease performance meet the standards. We avoid using non-standard products (such as thin sheaths or low-quality grease) that could compromise product lifespan. We can provide third-party testing reports (such as SGS) for each batch to verify strength and elongation data, preventing future stress fractures caused by insufficient base material strength or poor toughness.

- We prioritize products with additional anti-corrosion layers (such as galvanizing the steel strand base material, then applying grease and then sheathing) to create a multi-layered anti-corrosion barrier and further enhance corrosion resistance. Our HDPE sheaths are preferably 1.2-1.5mm thick (higher than the national standard minimum of 1.0mm), made from first-grade HDPE, and contain UV inhibitors. They pass the "bend test" and show no cracking. We use specialized anti-corrosion grease to ensure a continuous seal in year-round environments.

4. Regular Inspection and Maintenance

- After commissioning, inspect the structure housing the steel strands (such as floor slabs and beams) annually for cracks and leaks. If rainwater or corrosive liquids come into contact with the strands, promptly address the problem and repair the sheathing. If localized sheath damage (≤5mm in diameter) is detected, fill the damaged area with a special repair adhesive and then seal it with anti-corrosion tape. If the damage is extensive, replace the entire strand immediately.

- Every 3-5 years, inspect the HDPE sheathing for cracks, aging, or brittleness. For severely aged areas, apply a special anti-corrosion coating for secondary protection. Also, inspect the anchor seals at the tensioning ends to ensure they are free of rust. If stress loss exceeds 10% or internal rust depth is ≥0.1mm, implement reinforcement measures (such as additional tensioning or adding a protective layer) to prevent further damage.

In a word, extending the service life of unbonded steel strands requires more than a single effort; it requires a comprehensive combination of product selection, standardized construction, regular maintenance, and professional support. As a supplier with years of experience in the prestressed concrete industry and our own factory, we not only provide qualified products but also offer professional guidance in procurement, construction, and maintenance, indirectly extending the service life of steel strands. Only by ensuring effective control at every step throughout the entire lifecycle can we maximize the value of steel strands and ensure the long-term safety and stability of engineering structures. For product test reports or customized engineering solutions, please contact us by phone or email on our official website, ensuring the long-term safety and stability of engineering structures.