ALL YOU WANT TO KNOW ABOUT STEEL REINFORCEMENT BARS

ALL YOU WANT TO KNOW ABOUT STEEL REINFORCEMENT BARS

STEEL REINFORCEMENT BARS

Also known as reinforcement steel, reinforcing steel and reinforcing steel is a steel rod or mesh of steel rods used in reinforced concrete and masonry structures to reinforce and hold tension. The reinforcement surface is often designed to improve the quality of bonding with concrete.

GRADES OF REBAR INDIFFERENT CODES

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TYPES REINFORCEMENT BARS

PLAIN REBAR

1.  CARBON STEEL

2.  MILD STEEL

Reference: I.S. 432-part 1 -1982.

Generally, steel is referred to as carbon steel, where the main alloy component used is carbon and no other basic requirements are specified; Namely, chromium, cobalt, nickel. Carbon steel can be divided into two categories: high and low carbon steel. As the names suggest, high-carbon steel has high levels of carbon, while low-carbon steel has a low percentage of carbon. Mild steel is a form of low carbon steel. The main difference between carbon steel and mild steel is that carbon steel has a high amount of carbon, while mild steel has low levels of carbon.

Difference Between Carbon Steel And Mild Steel

Definition

1.     In general, Carbon Steel has a higher amount of carbon.

2.     Mild Steel has a relatively low amount of carbon.

Carbon Content

1.    Carbon steel can have weight percentages of carbon ranging from 0.05-1.70%.

2.    Mild Steel has a carbon content of 0.05-0.25% by weight.

Price

1.    Carbon Steel is more expensive.

2.    Mild Steel is cheaper

Properties

1.  Carbon Steel is stronger than Mild Steel. It is also brittle and can break easily when compared to Mild Steel.

2.    Mild Steel can be easily welded into different shapes due to its softer and weaker properties.

Heat Treatment

1.    Carbon Steel can successfully undergo heat treatments.

2.    Mild Steel cannot successfully undergo heat treatments.

DEFORMED BAR

1.  THERMO MECHANICALLY TREATED (TMT)  BAR

Reference: I.S.1786- 1985

TMT is short for Thermo Mechanically Treated bars. These are reinforcement bars known for high strength. The characteristic feature of these bars is the soft inner core covered with a hard outer surface. They are manufactured under a process called Thermo Mechanical Treatment, after which they are labelled, where hot steel billets are passed through cold water. This technique hardens the outer surface, improves its tensile strength, while the core is at a higher temperature and increases the dilution. This change in microstructure across the bar's cross-section gives it immense strength. Also, the TMD bars do not undergo any deformation or winding processes, so the TMD bars have no surface cracks or other defects.

2.  HIGH YIELDING STRENGTH DEFORMED HYSD BARS

Reference: I.S.1786- 1985

HYSD, or High Yielding Strength Deformed Steel goes through heat treatments much like TMT bars, but the steps following this are completely different. Subsequent to the heat treatment procedure, the heated rods are shaped through heat rolling or cold twisting. Thus HYSD rods are also subjected to various kinds of mechanical and thermal treatments.

3.  TOR BAR

Reference: I.S.1786- 1985

The technical term for TOR (Toristeg Steel Corporation of Luxembourg) is CTD, which when expanded means cold-formed steel. It is a form of HYSD steel, where the steel bars, after undergoing the mandatory heat treatment process, are twisted and deformed cold. These deformations are present on the surface and are carried out after an elongation process, which confers a greater elastic limit on the steel and the surface deformations impart a greater bond with the concrete. Due to deformations, these bars minimize slippage in the concrete and increase the bond between the two materials. Deformed bars have a higher tensile strength than MS steel bars, and the deformations must be evenly spaced along the bar.

The TMT and TOR steel bars are high strength, but the TMT bars are still considerably stronger. Due to their superior strength and high resistance to corrosion, TMT bars are the number one preference for coastal construction, where extreme humidity is a big problem. TOR is a good general-purpose steel bar.

REASONS TO PICK TMT BARS OVER TOR AND HYSD STEEL BARS:

1. TMT bars lack torsional stress as they do not undergo physical deformation. Therefore, the chances of surface defects are almost negligible.

2. Reducing surface defects means TMT bars are less prone to harmful oxidation, such as corrosion, compared to HYSD bars

3. TMT bars are more affordable. This is because they do not go through additional hardening processes; water cooling methods harden the TMT bar sufficiently. This reduces the energy and money spent on deformation processes, increasing its affordability. Additionally, TMT bars use 8-11% less steel compared to HYSD bars, further enhancing their affordability.

4. The use of TMT bars for construction helps reduce steel consumption by 8% to 11% compared to HYSD bars for the same construction, again increasing its accessibility.

5. Because TMT bars have a uniform and hardened periphery and a considerably softer core, these types of bars will have the desired tensile strengths, along with high elongation and ductility, as needed in the construction of buildings located in areas with regular seismic activity.

4.  CORROSION-RESISTANT  STEEL  BARS

TOR steel bars are also manufactured with the addition of a small amount of copper and chrome and are identified as CRS (Corrosion Resistant Steel) bars and also HCR (High Corrosion Resistance) bars. The manufacturers of these steels claim that these bars resist corrosion; however, the claims are disputed by various users and laboratories. They cost approximately 2-3% more than TOR steel bars.

OTHER TYPES OF REBARS

Depending upon the type of material used in the production of rebar, different types of rebars are

1. European Rebar

2. Carbon Steel Rebar

3. Epoxy-Coated Rebar

4. Galvanized Rebar

5. Glass-Fiber-Reinforced-Polymer (GFRP)

6. Stainless Steel Rebar

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Why do we use deformed bars in concrete?

Deformed reinforcement bars are the standard reinforcement for concrete reinforcement. Reinforcement bars are used because the concrete has good compressive strength but little shear strength, so the weight of a column or beam together with the load may cause the concrete to fail to support the design load.

Rebars are corroded to give the hardened concrete more area to grip. A soft bar allows movement in hardened concrete, which ultimately, breaks, but prevents it from moving, compared to concrete, with broken bars, small handles or ribs. These ribs form two pieces, and when held together, are less likely to slip, so they hold their positions better.

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