Friday, May 29, 2020

What is a Rebar? Types and Grades of Steel Reinforcement


Rebars

What is a Rebar?

Rebars are the steel reinforcement bars which are used in construction due to its resistance to the Tensile strength. 

In RCC , concrete tends to have a good resistance to Compression strength but when it come to tensile strength, concrete fails. To overcome this issue steel reinforcements are provided in concrete which improves the tensile strength of the construction.

Steel is used because the elongation of steel due to high temperature which can be said as thermal expansion coefficient is nearly equal to the concrete.

Carbon steel is most commonly used rebar, which consists of hot-rolled round bars with deformation patterns.

In working drawing at site, Rebars details are give as 

Example. 4no's, 16ø 250 cc
Which dentoes 4 number of rebars having centre to centre spacing of 16 diameter rebar.


Grades of Rebar in Different Codes & Sizes

India

Grades and sizes of bars used in Indian Standard (IS: 1786)
  • Grades- Fe 415, Fe 500, Fe 500D, Grade Fe 550
             whereFe - Ferrous material i.e. iron
                         415,500 etc - Yield Strength in N/mm2( Mpa)
                         D - Extra elongation/ Ductility 

Different sizes of Rebars used in India-
  • 6mm, 8mm, 10mm, 12mm, 16mm, 20mm, 25mm, 32mm, 36mm 
  • Bars like 40mm, 50mm , 60mm are directly ordered on factories.
America

Grades and sizes of bars used in American Standard (ASTM A 615)
  • Grade 75 (520), Grade 80 (550) 
Different sizes of Rebars used in America
  • 6mm, 10mm, 13mm, 16mm, 19mm, 2mm, 25mm, 29mm, 32mm, 36mm, 43mm, 57mm
Europe

Grades and sizes of bars used in Euro Standard(DIN 488)
  • BST 500 S, BST 500 M
Different sizes of Rebars used in Europe
  • 6mm, 8mm, 10mm, 12mm, 14mm, 16mm 20mm 25mm, 28mm, 32mm, 40mm, 50mm.
Australia

Grades and sizes of bars used in Australian Standards AS/NZS4671-2001
  • 250N, 300E, 500L, 500N, 500E (Mpa)
Different sizes of Rebars used in Australia
  • 12mm, 16mm, 20mm, 24mm, 28mm, 32mm, 36mm.
British

Grades and sizes of bars used in British Standard BS4449: 1997
  • GR 460 A, GR 460 B 
Now, We will see different types of Steel reinforcements,

The steel reinforcement used in concrete construction is of 4 types

Hot Rolled Deformed Steel Bars


  • Hot rolled deformed bars are most commonly used steel reinforcement for R.C.C structures.
  • They have ribs on the surface
  • They are of different types such as :- TMT (Thermo mechanically treated), HYSD (High yield strength deformed bars)
Cold Worked Steel Bars


  • They are obtained by putting the hot rolled deformed steel bars into cold water.
  • This lets the bars twist.
  • The process is done at room temperature and since the bar dont show plastic yield, it is considered as less ductile compared to hot rolled deformed steel bars.
Mild Steel Plain Bars

  • These bars show plain surface.
  • Bars dont have ribs on the surface.
  • They are used in small projects , not on heavy structures.
Pre-stressing Steel Bars


  • Commonly known as strands or tendons (made of 2-7 wires).
  • Multiple tendons are used and pre-stressing is carried out.


We will discuss more about Steel Reinforcements in concrete structures in next article.

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