Product Name
Grade III Rebar (High-Strength Deformed Reinforcing Bar)
1. Overview
Grade III Rebar is a high-strength, ribbed (deformed) steel bar used as reinforcement in reinforced concrete structures that require high load-bearing capacity, superior bond strength, and reliable ductility. It represents a significant improvement over Grade I (mild) and Grade II (medium-strength) bars in terms of yield strength, tensile capacity, and fatigue performance.
Grade III reinforcement is widely used in high-rise buildings, bridges, highways, industrial plants, and seismic-resistant structures, where both strength and ductility are critical. Depending on the national standard, Grade III generally corresponds to modern rebar designations such as HRB400 / HRB500 (China), Fe500 / Fe550 (India), or Grade 60 / 75 (U.S.).
2. Material Classification and Standards
"Grade III" is a classification commonly used in older or local systems; the specific mechanical requirements depend on the applicable national standard. Below are equivalent standards and grades used internationally:
| Region/Standard | Equivalent Grade | Yield Strength (approx.) | Notes |
|---|---|---|---|
| China (GB 1499) | HRB400 / HRB500 | 400–500 MPa | High-strength ribbed bar |
| USA (ASTM A615) | Grade 60 / Grade 75 | 420–520 MPa | Widely used in concrete structures |
| Europe (EN 10080) | B500B / B500C | 500 MPa | Good ductility for seismic design |
| India (IS 1786) | Fe500 / Fe550 | 500–550 MPa | High ductility and fatigue life |
| Japan (JIS G3112) | SD390 / SD490 | 390–490 MPa | For reinforced and prestressed concrete |
Always specify the standard reference and mechanical requirements instead of the generic term "Grade III."
3. Mechanical and Physical Properties
Typical ranges for Grade III / high-strength deformed rebar (exact values vary by standard):
Yield strength (fy): 400–550 MPa
Tensile strength (fu): 540–650 MPa
Elongation: ≥ 10–16%
Elastic modulus: ~200 GPa
Density: 7,850 kg/m³
Form: Deformed (ribbed) surface for superior mechanical bond with concrete
Ductility: Enhanced over Grade II, suitable for seismic and cyclic loading
Grade III bars exhibit excellent bond behavior, high energy absorption, and consistent weldability when low-carbon steel chemistry is used.
4. Dimensions and Supply Range
Nominal diameters: 6 mm – 50 mm
Common diameters: 8, 10, 12, 16, 20, 25, 28, 32, 40 mm
Lengths: 6 m / 9 m / 12 m (standard); custom cut-to-length available
Surface finish:
Mill black (as-rolled)
Epoxy coated (for marine or chemical environments)
Hot-dip galvanized (for corrosion resistance)
Stainless steel (for extreme durability applications)
Tolerances: Per standard (typically ±0.5–1% in diameter; ±50 mm in length)
5. Key Features and Advantages
High Strength-to-Weight Ratio: Allows reduced bar sizes or spacing without compromising structural integrity.
Excellent Bond Strength: Ribbed profile provides high friction and mechanical anchorage in concrete.
Improved Ductility: Retains elongation even at higher yield strength levels, ideal for seismic regions.
Fatigue and Impact Resistance: Suitable for dynamic load applications (bridges, industrial floors).
Good Weldability and Formability: For low-carbon variants or controlled chemical composition grades.
Economical Structural Design: Reduces steel consumption and concrete cover thickness.
6. Typical Applications
Reinforced concrete columns, beams, slabs, and shear walls in high-rise buildings
Bridges, flyovers, tunnels, and retaining walls
Industrial and marine structures exposed to fatigue or corrosion
Seismic-resistant frames and retrofitting projects
Infrastructure and foundation works (piles, caissons, pile caps)
7. Calculation Example – Weight per Meter
To estimate mass per meter, use:
[
m = \rho \times \frac{\pi d^2}{4} \times 10^{-6} \times 1000 = 0.006165 \times d^2
]
(where d = bar diameter in mm)
Example: For a 16 mm Grade III rebar:
[
m = 0.006165 \times (16)^2 = 0.006165 \times 256 = 1.578\text{ kg/m}
]
Thus, one 12 m bar weighs approximately:
1.578 × 12 = 18.94 kg
Reference weights per metre:
10 mm = 0.617 kg/m
12 mm = 0.888 kg/m
16 mm = 1.578 kg/m
20 mm = 2.466 kg/m
25 mm = 3.854 kg/m
32 mm = 6.313 kg/m
8. Fabrication, Handling, and Welding
Bending: Cold bending permitted per standard; maintain minimum bend diameters (e.g., 4–6× bar diameter).
Cutting: Mechanical shears or abrasive saws; flame cutting not recommended for coated bars.
Welding: Only weld grades designated "Weldable" (e.g., ASTM A706, HRB400E). Verify chemistry and preheat as needed.
Storage: Keep off the ground and covered to prevent rust; use timber spacers between layers.
Placement: Clean free of oil, mud, or scale before concrete placement.
9. Quality Assurance and Inspection
Mill Test Certificate (MTC) required for all shipments: chemical composition, yield/tensile strength, elongation.
Routine tests: Tensile, bend/rebend, and elongation.
Coating inspection: DFT, adhesion, and holiday detection for epoxy or galvanizing.
Optional tests: Impact, fatigue, weldability, and macrostructure.
Third-party inspection: Available for government, EPC, or infrastructure projects.
10. Packaging and Delivery
Bundled and tagged with:
Grade and standard (e.g., HRB400 / ASTM A615 Grade 60)
Diameter, length, and weight
Heat/lot number for traceability
Export packing: seaworthy with waterproof wrapping, strapped bundles, edge protection, and labeled for project tracking.
11. Ordering Checklist
Provide these details to ensure precise delivery:
Applicable Standard: e.g., GB1499.2-2018 HRB400 / ASTM A615 Grade 60 / EN 10080 B500B.
Mechanical Requirements: yield, tensile, elongation, ductility class.
Bar Size and Quantity: diameters, lengths, total tonnage or bar count.
Surface Finish: black / galvanized / epoxy coated / stainless.
Weldability / Seismic Requirements: specify if HRB400E / Grade 60W (low-carbon).
Inspection Needs: MTC, third-party witness, bending test, coating inspection.
Packaging & Delivery: bundle weight limits, export marking, and certification requirements.
12. Typical Comparison Table
| Property | Grade I | Grade II | Grade III |
|---|---|---|---|
| Yield Strength | ~235 MPa | 300–400 MPa | 400–550 MPa |
| Surface Type | Plain / Smooth | Deformed | Deformed (ribbed) |
| Ductility | High | Moderate | High (controlled) |
| Bond to Concrete | Low | Good | Excellent |
| Typical Use | Stirrups / ties | General RC | Primary structural members |
13. Advantages of Using Grade III Rebar
✅ Reduces steel consumption by up to 20–25% compared with lower grades.
✅ Ensures better earthquake resistance due to controlled elongation and ductility.
✅ Offers higher load capacity without increasing section size.
✅ Supports modern mechanized fabrication and bending machines.
✅ Widely available from mills with consistent quality certifications.
14. Recommended Standards for Procurement
GB/T 1499.2–2018: Hot Rolled Ribbed Bars for Reinforcement (HRB400 / HRB500).
ASTM A615/A706: Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement.
EN 10080: Steel for the Reinforcement of Concrete.
IS 1786: High Strength Deformed Steel Bars and Wires for Concrete Reinforcement.
JIS G3112: Steel Bars for Concrete Reinforcement (SD390 / SD490).
15. Conclusion
Grade III Rebar provides the ideal balance of high strength, ductility, and economy for modern reinforced concrete structures. Its superior bond performance and energy absorption make it indispensable in earthquake-resistant design and high-load construction. By specifying the correct standard and mechanical properties, designers ensure safety, reliability, and long-term durability in every application.
Would you like me to create a technical datasheet table for Grade III Rebar (listing diameters, weight/m, and standard mechanical properties for HRB400 and HRB500)? It's ideal for quoting or exporting.
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