The Ultimate Guide to Steel Rebars Size and their Types

Civil Engineer / Content Writer

Concrete is a construction material that is sufficiently strong in compression, but weak in tension. Hence, concrete is reinforced with steel, because it has good tensile strength and bond between steel and concrete is also good.

The steel bars that are incorporated/reinforced in concrete to impart tensile strength into concrete are known as steel rebars. Rebar is reinforcing bar.  Steel bars are used as rebars because elongation of steel due to high temperatures (thermal expansion coefficient) nearly equals to that of concrete.

0303040002-01-Reinforcement-Steel-Fixing
Courtesy - Pixabay

Also Read:

Material Buying Guide for Steel Bars

Types of Steel Rebars:

There are two types of steel bars available in the market:

  • Plain Steel bars – Mild steel and Medium tensile steel bars
  • Deformed bars (Irregular Surface) – High Strength Deformed (HSD) bars

01. Plain Steel Bars:

It Should conform to IS 432 Part I specifications in India. These steel rebars are plain in surface and round sections. Easy to cut and bend.

Courtesy - gtbsteel

Mild Steel Bar Grades (as per IS: 432, part – I – 1982)

Mild Steel Bars

Medium Tensile Steel Bars

Grades
  • Grade I designated as Fe 410-S or Grade 60
  • Grade II designated as Fe 410-O or Grade 40
  • Fe-540-w-ht or Grade 75

02. Deformed Steel Bars:

Should conform to IS 1786 specifications. These are HYSD (High Yield Strength Deformed bars) bars having lugs, ribs or deformation on their surface, reducing slippage in concrete and increasing the bonding between concrete and steel. Deformed Steel bars have better properties than plain steel bars.

Ribbed or Tor Steel Bars

TMT Bars

About
  • Cold twisted deformed bar
  • Cold treated bar
  • The bars are twisted single or double i.e. two bars twisted together spirally against each other.
  • The stresses developed during twisting, increases the yield stress of bars.
  • Thermo Mechanically Treated bars
  • Hot treated bar
  • Here, hot bars coming out of last rolling mill stand are rapidly quenched by a special water spray system, there by cooling and hardening outer surface. The inner core is allowed to cool naturally, forming a composite material of ductile inner core and tough outer surface
  • Rapid cooling of surface provides unique combination of strength and ductility
0303040002-03-Tor-Bars
Courtesy - Sikandersteels
0303040002-04-TMT-Bars
Courtesy - Alaknanda

Popular Grades of High Strength Steel Bars worldwide both Tor and TMT are listed below:

Popular Grades

American Standard   (ASTM A 615) Euro Standard        (DIN 488) British Standard BS4449: 1997 Indian Standard       (IS: 1786)
Grade 75 (520) BST 500 S GR 460 A Grade Fe – 415, Fe – 500, Fe – 500D
Grade 80 (550) BST 500 M GR 460 B Grade Fe – 550

In Fe – 500D, D stands for Ductility. These bars are more ductile than Fe – 500.

Size of Steel Rebars:

Rebars are supplied in U-bent or straight rods of 40ft in length.

Size Weight per Bundle Rods per Bundle
8 mm 1 Bundle 47.41 kg 10
10 mm 1 Bundle 51.85 kg 7
12 mm 1 Bundle 53.33 kg 5
16 mm 1 Bundle 56.89 kg 3
20 mm 1 Bundle 59.26 kg 2
25 mm 1 Bundle 46.30 kg 1
32 mm 1 Bundle 75.85 kg 1
  • Weight Tolerance: As per IS: 1786-2008
8mm to 10mm ± 7%
12mm to 16mm ± 5%
20mm ± 3%

For E.g: 8mm bundle may vary from 44.09 to 50.73 kgs and still be safe

  • Standard rod length: 12 meters (40 ft)
  • Weight of 1 rod = {(Dia x Dia)/162} x 12 (in kg)

Dia = Diameter in mm

Most commonly used rebar these days is TMT bar. TMT process changes the structure of material to a composite structure with tough surface rim and soft (ductile here) core providing an optimum combination of high strength, ductility and bendability.

TMT saves steel consumption as well as cost. If a structure has 1000 tons of M.S reinforcement than using TMT bars reduces the steel consumption to 400 tons saving 600 tons of steel with no compromise in the strength of structure. Reduction in steel reduces the considerable cost of structure.

Also Read:

Different Types of Cement and Their Purposes
Why Aggregate has an Important Role in Concrete

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