AS/NZS 4671: Steel Reinforcing Bars — Grades 250N, 300E, 500L, 500N, and 500E

Quick Answer

AS/NZS 4671 is the primary Australian and New Zealand standard for steel reinforcing bars (rebar) used in reinforced concrete structures. It covers deformed bars, plain round bars, and coiled reinforcing bar, specifying chemical composition, mechanical properties, geometrical requirements (rib pattern, cross-sectional area), mass per metre, and bend/rebend test requirements. The standard also defines ductility classes — N (normal), E (seismic/earthquake), and L (low ductility) — which govern the choice of grade for different structural and seismic exposure categories under AS 3600 (Concrete Structures) and NZS 3101 (Concrete Structures NZ).

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Scope and Applicability

AS/NZS 4671 applies to:

• Deformed (ribbed) reinforcing bars in nominal bar sizes 6 mm to 50 mm diameter
• Plain round bars (smooth) used as fitments and ties
• Coiled (coil) reinforcing bar in sizes 6 mm to 16 mm
• Weldable reinforcing steel for use in reinforced concrete
• Material for standard and seismic ductility applications

The standard does not cover:

• Prestressing strand or wire (refer AS 1085.1, AS 1085.3)
• Stainless steel reinforcing bars
• Fibre-reinforced polymer (FRP) reinforcing bars
• Welded wire mesh (refer AS/NZS 4671 covers individual bars only; mesh is separately specified)

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Grade Coverage and Ductility Classes

Key distinctions:

• Ductility Class E grades (300E, 500E) have both a minimum AND maximum Rm/ReH ratio, ensuring the steel is neither too brittle nor too strong relative to its yield — critical for seismic design where overstrength in reinforcement can shift failure modes to less ductile elements.
• Ductility Class L (500L) is a low-ductility grade restricted to applications where plastic rotation is not required. AS 3600 prohibits Class L reinforcement in seismic zones or as primary flexural reinforcement in ductile frames.
• 500E with Agt ≥ 10% allows the concrete section to undergo significant plastic deformation in an earthquake event without fracture of the reinforcement.

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Chemical Composition Requirements

All values are wt% maximum unless noted. Ladle analysis applies.

Grade 250N

Grade 300E

Grade 500L

Grade 500N

Grade 500E

CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15. Microalloying elements Nb, V, and Ti may be used to achieve the required strength levels. When welded connections are required, the CEV limit governs weldability per AS/NZS 1554.3 (welding of reinforcing steel). N max of 0.012% applies to all grades.

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Mechanical Properties

All tensile tests per AS 1391. Agt (total elongation at maximum force) is measured on the reduced-section gauge length before fracture. Rm/ReH is the ratio of tensile strength to upper yield strength (or Rp0.2 when no distinct yield point exists).

Grade 250N

Grade 300E

Grade 500L

Grade 500N

Grade 500E

Bend test mandrel diameters listed are for sizes 10–16 mm. Larger bar diameters require larger mandrel multiples per AS/NZS 4671 Table. Rebend tests (bend 90°, rest 1 hour at 100 °C, rebend back to original) are also required and the bar must not fracture.

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Nominal Bar Sizes and Mass per Metre

Mass tolerance per AS/NZS 4671: individual bar ±6%, lot average ±4.5%.

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Geometrical Requirements (Deformed Bars)

Deformed bars must have transverse ribs (lugs) and may have longitudinal ribs to enhance bond with concrete.

Bar markings identify the manufacturer, country of origin, grade, and ductility class. For Grade 500E, the letter E must appear in the rib marking to distinguish it from Grade 500N on site.

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ACRS Certification Requirements

ACRS (Australasian Certification Authority for Reinforcing and Structural Steels) certification is the recognised independent third-party certification scheme for reinforcing steel in Australia and New Zealand. For AS/NZS 4671 product:

• ACRS provides certification at two levels: steelmaker (mill) certification and processor certification
• Certification involves annual audits, surveillance testing, and independent verification of chemical and mechanical test results
• All major Australian states' building regulations and infrastructure project specifications require ACRS-certified reinforcing steel
• The National Construction Code (NCC) effectively mandates ACRS certification for structural reinforcing bar through reference to AS 3600
• Imported rebar must also be ACRS-certified; many projects have experienced non-compliant imported bar being rejected without ACRS certification

The ACRS certificate must be current at the time of supply and must list the specific grade(s) certified (e.g., ACRS certification for 500N does not cover 500E supply).

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Cross-Standard Equivalents

Note: ASTM A615 Grade 60 (420 MPa yield) and A706 Grade 60 (weldable seismic) are the closest US equivalents. A706 is comparable to 500E in ductility requirements (Rm/ReH ≥ 1.25, Agt ≥ 14%) but has a lower yield strength base. A615 Grade 80 (550 MPa) exceeds 500N/500E in strength but has no ductility ratio or Agt requirement.

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MTC Verification Checklist

• Standard shown as AS/NZS 4671
• Grade and ductility class match purchase order (e.g., 500E, not just 500)
• Bar sizes match ordered product; nominal mass per metre within tolerance
• Heat (cast) number traceable to physical bar markings
• C, Mn, P, S, CEV within grade limits
• ReH ≥ grade minimum
• Rm ≥ grade minimum
• Rm/ReH ratio within required range (especially critical for 500E: 1.15 to 1.40)
• Agt ≥ grade minimum (critical for 500E: ≥ 10%; 500N: ≥ 5%)
• Bend and rebend test results — no fracture
• Bar markings description confirms ductility class identification
• ACRS certificate number, grade(s) covered, and expiry date noted
• MTC signed by authorised mill representative

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Frequently Asked Questions