JG/T 161-2016 Unbonded Prestressing Steel Strand

Standard Overview

JG/T 161-2016 Unbonded prestressing steel strand is a building industry standard of the People's Republic of China, issued by the Ministry of Housing and Urban-Rural Development on 2016-11-15 and implemented on 2017-05-01, replacing JG/T 161-2004. It specifies the terms and definitions, symbols, marking, general requirements, requirements, test methods, inspection rules, marking, packaging, quality document, transport and storage of unbonded prestressing steel strand.

Scope

The standard applies to unbonded prestressing steel strand used in post-tensioned prestressed concrete structures.

Key Definitions

• Unbonded prestressing steel strand: prestressing strand whose surface is coated with an anti-corrosion lubricating coating and wrapped with a sheathing, allowing permanent relative movement between the strand and the sheathing.
• Prestressing steel strand: strand stranded from cold-drawn plain round steel wires.
• Anti-corrosion lubricating coating: coating applied to the strand surface to prevent corrosion and reduce friction between the strand and the sheathing.
• Sheathing: tube wrapped outside the strand and coating to protect the strand from corrosion and prevent bonding with the surrounding concrete.

Main Requirements

Specifications and Performance

• Nominal diameters: 12.7 mm, 15.2 mm and 15.7 mm; nominal cross-sections: 98.7 mm², 140.0 mm² and 150.0 mm².
• Nominal tensile strengths: 1720 MPa, 1860 MPa and 1960 MPa.
• Anti-corrosion grease content: ≥ 43 g/m (12.7 mm), ≥ 50 g/m (15.2 mm), ≥ 53 g/m (15.7 mm).
• Sheathing thickness: ≥ 1.0 mm; friction coefficients: κ ≤ 0.004 and μ ≤ 0.09.

Appearance and Materials

• The sheathing surface shall be smooth, free of dents, visible strand contours, bubbles, mechanical damage, cracks and obvious creases.
• The strand shall comply with GB/T 5224; its surface must be properly protected from rust and corrosive media before coating.
• The anti-corrosion grease shall comply with JG/T 430, with good chemical stability, water resistance and lubricity — not flowing at high temperature and not embrittling at low temperature.
• The sheathing shall be made of high-density polyethylene with a density of 0.942–0.965 g/cm³ complying with GB/T 11115; no fillers affecting performance are allowed.
• Sheathing tensile properties: tensile yield stress ≥ 15 MPa; nominal tensile strain at break ≥ 400%.

Inspection Rules

• Inspection is divided into delivery inspection and type inspection; type inspection applies to new products, major process/material changes, resumed production, etc.
• Batch: each batch of the same nominal tensile strength, nominal diameter and production process shall not exceed 60 t.
• Sampling: appearance on every coil; strand diameter, mechanical properties and elongation on 3 samples per batch; grease content and sheath thickness on 3 samples; sheath tensile properties on 5 samples.
• If any delivery inspection item fails, the affected coil is rejected and double samples are retested; if any retest item still fails, the batch is rejected.

Marking, Packaging and Storage

• Each coil carries a metal tag with the producer, product name, nominal tensile strength, nominal diameter, net weight, coil number, standard number and production date or batch number.
• Products should be coiled or wound on reels with effective protection during normal transport; coil diameter not less than 1.0 m.
• During storage, products must not be placed in areas affected by heat and must be covered with rain-proof sheets; stacked products should not be stored beneath heated prestressing strand.

Original Document

The full original standard document (Chinese) is available for download:

Download JG/T 161-2016 (PDF)