Introduction
In the world of civil engineering, steel reinforcement plays a vital role in ensuring the durability and strength of concrete structures. It is the most widely used material in the field of construction. If you want to reinforce your skills and strengthen yourself then here you will get detailed information about steel reinforcement.
Definition of Steel Reinforcement
Steel reinforcement is the steel bars that are embedded material of the reinforced cement concrete. The reinforcement is provided in the form of bars or mesh. It transfers stresses from one material to another. It provides the tensile strength of the concrete.
Why do we need steel reinforcement?
Reinforcement is important in providing durability and tensile strength to the structure. As we know concrete is strong in compression but weak in tension. When the load acts upon the concrete, steel bars as reinforcement are provided to increase the tensile strength of the concrete. The composite hard mass obtained after combining both materials can withstand without compromising its stability. Both steel and concrete have nearly the same coefficient of thermal expansion thereby undergoing the same deformation under temperature variations. The reinforcement also prevents cracks from developing due to temperature and shrinkage stresses.
Suitability of Steel as Reinforcing Material
Many conventional materials, including bamboo and natural fibers, have been used in the past as reinforcement. However, it is determined that steel is the most suitable type of reinforcement. Steel is much stronger in tension, compression, shear, and torsion. Due to its ductile nature, it exhibits more elongation before failure occurs. The cutting bending and welding of steel can be conveniently done with commonly available tools and machines.
Types of Steel Reinforcement Bars
Steel bars are of the following types depending upon their availability and purpose:
Mild Steel Bars
Mild steel bars are smooth plain and rounded in shape. Due to very high ductility, it yields less strength and weak bonds. It has a low percentage of carbon ranging from 0.1% to 0.25%. Due to less strength, they are not preferred over high-yield strength deformed bars. They are used for nominal reinforcement work and as lateral ties in the column. These bars are highly prone to corrosion. The yield strength of mild steel bars is 40000 psi.
High Yield Strength Deformed Bars
These bars have a higher carbon percentage as compared to mild steel. These bars are of superior quality and strength. HYSD bars have two categories:
Hot-Rolled High-Yield Strength Bars
These bars have higher strength than mild steel bars. They have ribbed surfaces, providing a stronger bond with the concrete, making them suitable for structures exposed to heavy loads, and seismic and longitudinal movements.
Cold-Rolled High Yield Strength Bars
These bars are also called cold twisted deformed bars or Tor steel. These are formed by the process of twisting and deformation of mild steel bars. The crack and ribs are visible on the surface of cold twisted deformed bars, increasing the chances of corrosion. These have 50% higher yield stress than plain bars and do not show definite yield points. They are less ductile as compared to hot rolled bars.
Prestressing Steel bars
The prestressing reinforcement yields a very high strength than other types of reinforcement. This reinforcement is comprised of tendons, wire strands, or cables and bars. There will be very little prestress left after the losses in mild steel or HYSD bars, while the prestressing steel yields are very high elongation.
Tendons: Diameter 1.5mm to 8mm.
Wire Strands or Cables: These include a bundle of wires of a diameter range of 7mm to 17mm.
Bars: High tensile bars of diameter 10mm or more.
TMT Bars
These are called thermo-mechanically treated bars as they are processed through a thermo-mechanical treatment at a particular temperature. The cold water is passed on the hot rolled steel bars making the outer surface harder while the inner core is softer.
These bars are of superior quality and provide ductility, weldability, durability, and higher yield strength than mild steel bars. TMT bars are highly resistant to corrosion and seismic loads. Due to its improved properties, it is widely used in high-rise buildings, Dams, long-span bridges, underground structures, etc.
In India, SAIL (Steel Authority of India Ltd.) and TATA Steel are the producers of the TMT bars.
CRS Bars
With the advancement in research and development, there is the production of CRS or corrosion-resistant bars. They are highly resistant to corrosion and substantially designed to withstand marine or wet weather conditions. CRS bars are widely used in bridges, dams, industrial structures, and high-rise buildings.
Uses of Steel Reinforcement
The use of steel reinforcement is prevalent in various construction projects. Some of the common uses include:
- Reinforced Concrete Structures: Steel reinforcement is extensively used in constructing reinforced concrete beams, columns, slabs, and foundations, providing strength and durability to the overall structure.
- Bridges and Highways: Steel reinforcement is employed in the construction of bridges and highway pavements to withstand heavy traffic loads and dynamic forces.
- Retaining Walls: Retaining walls, which support soil or other materials, are reinforced with steel to prevent sliding or collapsing.
- Dams and Reservoirs: Provides strength and stability to large-scale hydraulic structures designed to regulate water flow, store water, and generate hydroelectric power.
Advantages of Steel Reinforcement
- Enhanced Strength: Steel reinforcement enhances the structural strength of the concrete, making buildings and structures more durable and resistant to various forces.
- Flexibility in Design: Steel reinforcement offers flexibility in design, allowing engineers to create complex shapes and structures without compromising on strength.
- Economy: Compared to other reinforcement materials, steel is relatively cost-effective, making it a popular choice in the construction industry.
- Fire Resistance: Concrete, when reinforced with steel, becomes more fire-resistant, increasing the safety of occupants during emergencies.
- Recycle: After a structure has served its purpose, any remaining steel reinforcement is recycled again and employed in new construction.
Disadvantages of Steel Reinforcement
- Susceptible to Corrosion: Steel reinforcement makes the structure significantly heavier, which may not be appropriate for some projects or locations with weak soil-carrying capability.
- High Thermal Conductivity: Steel has high thermal conductivity, which can lead to temperature-related expansion and contraction issues in certain environments.
- Heavy Weight: Steel reinforcement makes the structure significantly heavier, which may not be appropriate for some projects or locations with a weak bearing capacity of the soil.
- Expensive: Steel reinforcement is highly expensive, consequently increasing the cost of the structure.
FAQs
Can we weld steel reinforcement?
Yes, it can be easily welded to increase the bar lengths and at various joints.
Can steel reinforcement be used in all construction projects?
Steel is used as reinforcement in all reinforced concrete and steel structures due to its versatile properties.
What is the life span of the steel reinforcement before it starts to corrode?
It depends upon various factors, such as environmental conditions, exposure to moisture, and the quality of protective coatings. Proper protection and maintenance increase its durability and lifespan.
Conclusion:
Steel reinforcement is the backbone of modern construction practices. It provides strength and durability to the structures. Understanding the significance of steel reinforcement is important for engineers, architects, and anyone involved in the construction field. By involving it in our structures, we can build a safer, better, and more secure future for generations to come.
Also Read:
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