A steel bar is a long, cylindrical metal rod primarily used in construction and infrastructure for reinforcement in concrete structures. It provides tensile strength, durability, and structural integrity to the concrete, which is weak in tension but strong in compression.
Types of Steel Bars
- Mild Steel Bars (MS Bars)
- Smooth surface, plain in texture.
- Used for small-scale construction.
- Lacks strong bonding with concrete.
- Deformed Steel Bars (TMT and HYSD Bars)
- Ribbed or twisted surface for better bonding with concrete.
- Thermo-mechanically treated (TMT) bars are widely used for durability and strength.
- Rebars (Reinforcing Bars)
- Designed for reinforced concrete.
- Comes in various grades and diameters.
Parameters of Steel Bars
1. Diameter
- Refers to the thickness of the steel bar, measured in millimeters (mm).
- Common diameters: 6 mm, 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, and 32 mm.
2. Length
- Standard length: 12 meters (can vary depending on requirements).
3. Grades
- Steel bars are classified into grades based on yield strength.
- Fe 415: Yield strength of 415 MPa.
- Fe 500: Yield strength of 500 MPa (most commonly used).
- Fe 550: Higher strength for special structures.
- Fe 600: For high-stress areas like bridges and industrial structures.
4. Tensile Strength
- Maximum stress the bar can withstand while being stretched.
- Usually 1.08 to 1.15 times the yield strength.
5. Yield Strength
- Stress at which the steel begins to deform plastically.
- Denoted in MPa (Mega Pascal).
6. Elongation
- Percentage elongation determines ductility.
- Higher elongation indicates better ability to absorb shock and prevent sudden failure.
7. Weight of Steel Bar
- Calculated using the formula: weight in (kg/m) =(d*d)/162, d= diameter of bar
8. Bonding Strength
- The ability of the steel bar to adhere to concrete.
- Ribbed (TMT) bars provide better bonding compared to plain bars.
9. Corrosion Resistance
- Special coatings (e.g., epoxy) or alloying elements improve corrosion resistance.
10. Thermal Expansion
- Steel and concrete have similar coefficients of thermal expansion, ensuring uniform response to temperature changes.
11. Flexibility
- The ability to bend without cracking, essential for shaping during construction.
12. Carbon Content
- Impacts strength and ductility.
- Higher carbon increases strength but reduces ductility.
13. Surface Profile
- Ribbed bars enhance grip with concrete, reducing slippage under stress.
14. Chemical Composition
- Typical elements:
- Carbon (C): 0.15–0.25%
- Manganese (Mn): 0.5–1.5%
- Sulfur (S) and Phosphorus (P): <0.05% (low values prevent brittleness).
15. Fatigue Strength
- Resistance to cyclic loading over time.
IS Code Standards for Steel Bars
- IS 1786: Specifies requirements for high-strength deformed steel bars.
- IS 432: Covers mild steel and medium tensile steel bars.
Uses of Steel Bars
- Construction of Beams, Columns, and Slabs: For providing tensile strength.
- Reinforced Concrete Structures (RCC): Essential for high-rise buildings and bridges.
- Industrial and Infrastructure Projects: Dams, roads, flyovers, etc.