4.10 QUALITY CONTROL OF STEEL
Steel is a widely used structural material in reinforced concrete, steel frames, and masonry reinforcement. Quality control ensures strength, ductility, weldability, and durability, essential for structural safety and longevity.
4.10.1 Objectives of Steel Quality Control
- Ensure steel meets specified mechanical and chemical properties.
- Detect defects such as corrosion, cracks, and improper sizing.
- Confirm compliance with BIS / ASTM standards for structural performance.
- Ensure proper storage, handling, and bending practices.
4.10.2 Types of Steel Used in Construction
| Type |
Description / Typical Use |
| Mild Steel / TMT Bars |
Used in reinforced concrete for structural elements. |
| High Yield Strength Deformed (HYSD) Steel |
TMT bars with ribbed surface for better bonding with concrete. |
| Structural Steel Sections |
I, H, L, T sections used in steel frame construction. |
| Cold-rolled Steel |
Used for roofing sheets, cladding, light structures. |
4.10.3 Laboratory Quality Tests for Steel
| S. No. |
Test Name |
Description / Objective |
Typical Requirement / Acceptance Criteria |
Standard Reference |
| 1 |
Tensile Test |
Measures ultimate tensile strength, yield strength, elongation, and ductility |
Yield strength ≥ 415–500 MPa (depending on grade), elongation ≥ 14% |
IS 1786, ASTM A615 |
| 2 |
Bend Test |
Checks flexibility and absence of cracks upon bending |
No cracks when bent 180° over specified diameter |
IS 1786, ASTM A615 |
| 3 |
Chemical Composition Test |
Determines carbon, sulfur, phosphorus, and other alloy contents |
Carbon < 0.3% (for mild steel), limits as per grade |
IS 1786, ASTM A615 |
| 4 |
Rebar Surface Inspection |
Checks for rust, pitting, cracks, and uniform ribs |
Free from surface defects; uniform ribs |
IS 1786 |
| 5 |
Dimension & Tolerance Check |
Ensures specified diameter and length |
Diameter tolerance ±0.5 mm, length ±50 mm |
IS 1786 |
| 6 |
Corrosion Resistance Test |
Determines susceptibility to rust under standard conditions |
Minimal rusting under lab exposure or accelerated corrosion tests |
IS 1570, ASTM B117 |
| 7 |
Impact Test (Optional) |
Measures toughness at specified temperatures |
Meets grade-specific energy absorption |
IS 1757, ASTM E23 |
4.10.4 Field Quality Control Measures
- Proper Storage: Keep steel off the ground and covered to prevent rust.
- Handling: Avoid bending or dropping bars to prevent micro-cracks.
- Cutting and Bending: Follow recommended bending diameters to prevent fractures.
- Welding / Joining: Ensure compliance with approved welding procedures.
- Inspection: Check batch certificates from suppliers and verify test results before use.
4.10.5 Acceptance Criteria for Steel
| Property |
Mild Steel / TMT Bars |
Structural Steel Sections |
| Yield Strength |
≥ 415–500 MPa (depending on grade) |
≥ 250–350 MPa |
| Ultimate Tensile Strength |
485–620 MPa |
400–550 MPa |
| Elongation |
≥ 14% |
≥ 12% |
| Rib / Surface Quality |
Uniform ribs, free from cracks |
Smooth, free from rust and pitting |
| Diameter / Section Tolerance |
±0.5 mm |
As per IS / ASTM dimensional tables |
4.10.6 Important BIS / ASTM Standards (Latest Revision)
| Standard No. |
Title / Description |
| IS 1786 |
High Strength Deformed Steel Bars for Concrete Reinforcement |
| IS 432 |
Mild Steel and Medium Tensile Steel Bars – Specification |
| IS 1570 |
Methods for Accelerated Corrosion Testing of Steel |
| IS 2751 |
Hot-rolled Structural Steel Sections – T, I, L, Channels |
| ASTM A615 |
Standard Specification for Deformed and Plain Carbon-Steel Bars |
| ASTM A36 / A992 |
Structural Steel Shapes, Plates, and Bars |
| ASTM B117 |
Salt Spray (Fog) Corrosion Testing |
| ASTM E23 |
Charpy Impact Test for Metals |