Views: 0 Author: Site Editor Publish Time: 2026-02-24 Origin: Site
Plain PC wire, a high-tensile steel wire essential for prestressed concrete, comes with precise specifications to ensure performance in structures like bridges and beams. These standards define its strength, dimensions, and properties for safe, reliable use.
Plain PC wire features a smooth, uncoated surface that provides frictional bond with concrete, distinguishing it from indented or galvanized types. Made from high-carbon steel via cold drawing, it achieves tensile strengths of 1470-1860 MPa with low relaxation under load.
Manufacturers like TJ Wasungen supply it in coils for pre- or post-tensioned applications, emphasizing straight run-out and no joints for consistent stressing. Diameters range from 4-12mm, suiting diverse projects from sleepers to large spans.
Plain PC wire adheres to international standards like ASTM A421, BS 5896, GB/T 5223, EN 10138, IS 6003, and JIS G3536. These outline minimum tensile strength, relaxation limits, and testing protocols to prevent failures.
ASTM A421 focuses on stress-relieved wire for U.S. markets, requiring 80-90% ultimate load without breakage. BS 5896 specifies low-relaxation (≤2.5% at 1000 hours) for European use, while GB/T 5223 suits Asian precast production.
Common diameters include 4.00mm, 4.80mm, 5.00mm, 6.00mm, 7.00mm, and 9.00mm, with tolerances of ±0.05mm for precision fitting in molds. Smaller 4-5mm wires suit railway sleepers; 7-9mm handle bridge girders due to higher load capacity.
Nominal cross-sections vary: 18.7mm² for 5mm wire, up to 63.6mm² for 9mm, directly impacting breaking load calculations. Deviations beyond ±0.07mm risk uneven stressing or bond issues.
Grades are classified by minimum tensile strength: 1470 MPa (Grade 210), 1570 MPa (Grade 235), 1670 MPa (Grade 240), 1770 MPa (Grade 250), and 1860 MPa (Grade 270). A 7mm 1770 MPa wire yields ~68 kN breaking load, ideal for medium spans.
Yield strength sits at 80-90% of tensile (e.g., 1420 N/mm² for 1570 grade), with 0.2% proof stress ensuring no permanent deformation under service loads. Higher grades reduce wire volume by 10-15% but demand skilled tensioning.
Low-relaxation (LWR) is critical: ≤2.5% after 1000 hours at 70% ultimate stress per EN 10138, versus 8-10% for normal wire. This sustains prestress over 50+ years, minimizing camber loss in beams.
Class 1 (≤2.0%) suits long-term structures; Class 2 (≤3.5%) fits shorter spans. Testing involves loading coils at constant strain, measuring force drop.
Minimum elongation of 3.5-5% at rupture ensures ductility, preventing brittle failure during release. Bend tests require 4 bends over 20mm mandrel without cracks, confirming fatigue resistance.
Modulus of elasticity is 195-205 GPa, standard for steel, aiding precise jacking calculations. Poor ductility signals drawing flaws, rejecting batches.
Plain surface must be clean, scale-free, with max 12mm deviation over 1m length for straightness. No rust pits >0.1mm depth; coils weigh 1700-2400kg, outer diameter ≤2.3m for handling.
Packaging uses plastic-wrapped steel cores, labeled with grade, diameter, and lot number per ISO standards. TJ Wasungen offers custom coils for precast lines.
Grade (MPa) | Diameter Range (mm) | Min. Breaking Load (kN, 7mm) | Relaxation (%) | Best Use |
1470 | 4-9 | 56.5 | ≤3.5 | Sleepers |
1570 | 5-9 | 60.4 | ≤2.5 | Poles |
1670 | 6-9 | 64.3 | ≤2.5 | Beams |
1770 | 7-12 | 68.1 | ≤2.0 | Bridges |
1860 | 7-12 | 71.6 | ≤2.0 | High-load |
Higher grades excel in efficiency but cost more.
Tensile tests per ASTM E8 pull samples to failure, verifying strength and elongation. Relaxation per EN 10138 loads at 75% UTS for 1000 hours; straightness checked on 1m spans.
Batch rejection occurs if >1% fails; non-destructive magnetic testing detects surface flaws. Certifications include mill test reports (MTRs) tracing to heat numbers.
Match grade to design: 1570 MPa for standard precast, 1770+ for seismic zones. Consider environment—galvanized for corrosive sites per ASTM A475. Consult standards like PCI or FIP for application limits.
Suppliers like TJ Wasungen provide compliant stock; verify via independent labs. For Zeekweb clients, spec sheets boost SEO for "PC wire standards" searches.
New specs incorporate epoxy coatings for durability, reducing relaxation to <1.5%. Ultra-high-strength 2000 MPa wires emerge for lightweight designs, per ongoing ASTM updates. Sustainability focuses on recycled steel meeting EN 10138.
Digital tracking via QR-coded coils enhances traceability. Engineers should monitor BS and ASTM revisions for evolving tolerances.
