Generally there are two types of steel bars ("Sariya
" in hindi) available in the market.
Mild steel bars
Deformed steel bars
Steel bars used for construction work
(This Picture is Contributed by "Monu")
Mild steel bars (as per IS: 432, part-I -1982)
Mild steel bars are used for tensile stress of RCC (Reinforced cement concrete) slab beams etc. in reinforced cement concrete work. These steel bars are plain in surface and are round sections of diameter from 6 to 50 mm. These rods are manufactured in long lengths and can be cut quickly and be bent easily without damage.
Deformed steel bars (as per IS: 1786-1985)
As deformed bars are rods of steels provided with lugs, ribs or deformation on the surface of bar, these bars minimize slippage in concrete and increases the bond between the two materials. Deformed bars have more tensile stresses than that of mild steel plain bars. These bars can be used without end hooks. The deformation should be spaced along the bar at substantially uniform distances.
To limit cracks that may develop in reinforced concrete around mild steel bars due to stretching of bars and some lose of bond under load it is common to use deformed bars that have projecting ribs or are twisted to improve the bond with concrete. These bars are produced in sections from 6 mm to 50 mm dia.
In addition the strength of bonds of deformed bars calculated should be 40 to 80 % higher than that of plain round bars of same nominal size. And it has more tensile stress than that of plain round bars of same nominal size.
Cold twisted deformed (Ribbed or Tor Steel Bars) bars are recommended as best quality steel bars for construction work by structural Engineer.
Various Grades of Mild Steel Bars
Reinforcement bars in accordance with standard IS No. 432 part-I can be classified into following types.
1) Mild Steel Bars: Mild steel bars can be supplied in two grades
a)Mild steel bars grade-I designated as Fe 410-S or Grade 60
b) Mild steel bars grade-II designated as Fe-410-o or Grade 40
2) Medium Tensile Steel Bars designated as Fe- 540-w-ht or Grade 75
| S.No||Types of nominal size of bars || Ultimate Tensile Stress N/mm2minimum|| Yield Stress N/mm2|| Elongation Percent minimum|
| 1.||Mild Steel Grade I or Grade 60|| || || |
| || For bars up to 20mm|| 410||250 ||23 |
| || For bars above 20mm upto 50 mm|| 410||240 ||23 |
| 2.|| Mild Steel Grade-II or Grade 40|| || || |
| || For bar up to 20mm|| 370||225||23 |
| || For bars above 20mm upto 50 mm|| 370||215 ||23 |
| 3.||Medium Tensile Steel Grade-75 || || || |
| || for bars up to 16mm|| 540||350||20|
| || for bars above 16 mm up to 32 mm || 540||340 ||20 |
| || for bars above 32 mm up to 50 mm|| 510||330 ||20 |
Grade II Mild steel bar are not recommended for use in structures located in earth quake zones subject to severe damage and for structures subject to dynamic loading (other than wind loading) such as railways and highways bridges.
Every lot or consignment of mild steel bars brought at the site of work should be tested in laboratory before use in the work. However for small work one can use mild steel bars on the basis of verifying tests results made by manufacturer in his own laboratory; which are available with supplier.
Some of manufacturers stamped MS bars grade with their make /name and also give certification of test and grade. On the basis of the above information you can store mild steel bars grade-wise at the site of work.
Steel Bars for RCC Work
All finished steel bars for reinforced work should be neatly rolled to the dimension and weights as specified. They should be sound, free from cracks, surface flaws, laminations, rough, jagged and imperfect edges and other defects. It should be finished in a work manlike manner.
Column made of steel bars
(This Picture is Contributed by "Ahmed")
General precautions for steel bars in reinforcement
- Steel bars are clear, free from loose mil scales, dust and loose rust coats of paints, oil or other coatings which may destroy or reduce bond strength.
- Steel bars should be stored in such a way as to avoid distortion and to prevent deterioration and corrosion.
- Steel bars should not be clean by oily substance to remove the rust.
- The bar is bent correctly and accurately to the size and shape as shown in drawings.
- If possible, the bar of full length is used.
- Overlapping bars do not touch each other and these should be kept apart with concrete.
- The overlap if given should be staggered.
- The cranks in the bar at the end should be kept in position by using spots.
- The steel bars should not be disturbed while lying cements concrete.
- Required cover under steel bars should be given before laying the cement concrete.
- No over lap is given in the bar having a diameter more than 36 mm, if required, the bar should be welded.