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Reinforcing steel grades
What it is
Reinforcing steel grades define the yield strength and ductility of bars used in concrete.
Where it is used
Every reinforced concrete element: footings, columns, beams, slabs, walls, bridges, tanks and pavements.
How it works
Concrete is weak in tension, so steel bars are placed where tension develops. The ribs on high-strength deformed bars give mechanical interlock with concrete, so force passes between the two over a development length. The yield strength sets how much force a bar carries before yielding; the ductility (elongation and the ratio of tensile to yield strength) sets how much it can stretch and absorb energy before breaking, which matters most in earthquakes.
Types
- Fe 415 and Fe 415D
- Fe 500 and Fe 500D
- Fe 550 and Fe 550D
- Fe 600
- plain mild steel bars for ties and special uses
Materials
Carbon steel bars produced by hot rolling, often with quenching and self-tempering (thermo-mechanical treatment) that gives a hard outer layer and a tough core. Corrosion-resistant variants include epoxy-coated and stainless bars.
IS 1786 specifies high-strength deformed bars in India. The number in the grade is the minimum characteristic yield (0.2 percent proof) stress in MPa; the D grades have tighter chemistry and higher minimum elongation and tensile-to-yield ratio, and are preferred for ductile detailing to IS 13920. Design strengths, cover, lap lengths and anchorage come from IS 456. Comparable specifications elsewhere include ASTM A615, BS 4449, EN 10080, AS/NZS 4671 and CSA G30.18, each with its own grade names.
Installation and QA steps
- Check mill test certificates and the grade marking rolled on the bars
- Store bars off the ground, covered, and separated by grade and diameter
- Cut and bend cold to the bar bending schedule using the minimum mandrel diameters
- Tie with binding wire and support on cover blocks of the correct thickness
- Test samples for tensile strength, elongation and bend/rebend at the specified frequency
- Mixing grades on site
- Bending too tightly so bars crack
- Rebending already bent bars
- Heavy rust or oil reducing bond
- Cover blocks missing so bars lie on the formwork
Codes cited
- IS 1786 (India): High-strength deformed steel bars for concrete reinforcement.
- ASTM A615 (USA): Deformed and plain carbon-steel bars for concrete reinforcement.
- BS 4449 (UK): Steel for the reinforcement of concrete: weldable bar, coil and decoiled product.
- EN 10080 (Europe): Steel for the reinforcement of concrete: weldable reinforcing steel, general.
- AS/NZS 4671 (Australia): Steel for the reinforcement of concrete.
- CSA G30.18 (Canada): Carbon steel bars for concrete reinforcement.
Cited by number only. We do not reproduce code text, tables or figures.
Related
Squeezed versus pulled: why steel goes in concrete
Concrete is strong in compression, weak in tension; steel covers the gap.
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