Does the Thickness of the HDPE Sheathing of Unbonded Prestressed Steel Strand Affect its Service Life?

As the first protective barrier for unbonded steel strand, the thickness of the HDPE sheathing directly impacts the strand's physical protection and the integrity of its anti-corrosion system. It is a key factor affecting the service life of unbonded steel strand in construction projects. As the source manufacturer, we fully understand the importance of the sheathing and strictly adhere to production processes and standards to ensure its corrosion resistance, thereby guaranteeing the overall service life of the strand.

Ⅰ. Substandard Thickness

1. Weak Resistance to Mechanical Damage: In basic scenarios, the HDPE sheathing thickness should be ≥1.0mm. If this thickness does not meet the standard, the strand is susceptible to damage during transportation (due to friction and collision with tools) and installation (due to scratches and punctures from rebar and construction tools). Once damaged, corrosive media such as moisture and chloride ions can penetrate, first destroying the internal anti-corrosion grease and then corroding the strand, significantly shortening its service life. The originally designed service life of 50-100 years could be reduced to less than 30 years.

2. Decreased resistance to aging and environmental erosion: If the sheath thickness does not meet the standard, the steel strands stored in the open air for a long time or on the surface of the structure will not be able to effectively resist ultraviolet rays and will be prone to cracking and thinning. At the same time, alkaline substances in the concrete will also be more easily penetrated, directly destroying the anti-corrosion system and causing the protective function to fail prematurely.

II. Excessive Thickness

1. Construction and Heat Dissipation Issues: Excessively thick sheaths increase the difficulty of laying the steel strands. Furthermore, when energized, the strands generate heat (the permitted operating temperature of the conductor is 70°C). Excessively thick sheaths hinder heat dissipation, and prolonged high-temperature exposure accelerates sheath material aging, shortening their service life.

2. Stress Concentration Risk: In dynamic load scenarios, such as bridges, excessively thick sheaths can easily cause stress concentration when bent, potentially leading to weld cracking. While torsional stress can be relieved by installing a rotating device, this increases engineering complexity and cost, indirectly impacting overall structural stability.

III. Complying with Standard Thickness

1. Reducing the Risk of Breakage: According to JT/T 853-2013, the thickness of the HDPE sheath for unbonded steel strands must be controlled within 1.5 ± 0.5 mm and must be lubricated with an anti-corrosion grease of ≥ 50 g/m2 for optimal protection. This combination maximizes the anti-corrosion effect. The standard-compliant HDPE sheath provides a stable "protective barrier" for the steel strands, effectively resisting impact and friction, significantly reducing the risk of sheath damage.

2. Maintaining corrosion protection: The high-density polyethylene (HDPE) material used to make the sheath is UV-resistant and corrosion-resistant, continuously blocking corrosion from media such as moisture, chloride ions, and oxygen. This prevents the internal anti-corrosion grease from escaping and the steel strands from rusting, ensuring the continued effectiveness of the anti-corrosion system and ultimately ensuring the steel strands achieve their 50-100-year design lifespan, in keeping with the concrete structure.

In short, thickness control requires targeted adjustments for different scenarios. Regular inspections of sheath scratch depth (required to be ≤2mm or 20% of the pipe wall thickness) and joint strength are also necessary to prevent localized protection failures that could impact overall lifespan. HDPE sheath thickness significantly impacts the service life of unbonded steel strands. Our products not only support third-party testing but have also been validated in numerous large-scale bridge and high-rise building projects, ensuring the strands achieve a design lifespan of 50-100 years, safeguarding the safety and long-term value of the project structure. If you have purchasing needs, please contact us. We will provide reliable support for your project with our cost-effective, stable quality, and efficient service from our source factory.