Introduction
Steel round bars, also known as rebars or reinforcement bars, are long cylindrical rods made from steel that are commonly used in reinforced concrete structures like buildings, bridges, roads, and factories. Their high strength, ductility, and ability to bear tension make them an indispensable component in reinforced cement concrete structures. Steel circular bars help increase the load bearing capacity and improve the tensile strength of concrete which has high compressive strength but relatively low tensile strength.
Composition and Manufacturing of Steel Round Bars
Steel circular bars are made from low carbon steel containing around 0.25% carbon along with other alloying elements like manganese, silicon, chromium etc. to improve their mechanical properties. The steel is first melted in large electric arc furnaces and the desired chemical composition is achieved by adding ferrous and non-ferrous alloy additives. The molten steel is then continuously cast into bars or billets of desired cross-section and allowed to solidify. These bars further undergo multiple passes of hot and cold rolling processes to refine the microstructure and achieve the final diameter tolerances. The finished bars are then cut or rolled to the required lengths as per construction needs. Proper quality control checks ensure that the steel bars meet the specifications for use in reinforced concrete.
Usage and Types of Steel Round Bars
Steel circular bars find widespread application in the construction of concrete buildings, bridges, dams, roads etc. They act as the principal reinforcement and take up the tensile stresses that develop in structures. Depending on the diameter sizes, steel bars are designated as mild steel bars (10mm to 36mm), medium bars (40mm to 60mm) and high strength deformation bars. Mild steel bars are commonly used as primary reinforcement in structures having light to medium loading conditions. Deformed or twisted bars have projecting ribs that help achieve better bond with concrete compared to plain round bars. They allow structures to withstand higher loads and are preferred in heavily loaded elements. Epoxy coated rebars also offer corrosion protection in severely corrosive environments like marine structures.
Methods of Placement and Fixing of Steel Round Bars
Proper placement and binding of steel bars is important for developing their full tensile strength in reinforced concrete elements. The bars are firmly held in position using bar binders or mild steel wires at intersection points before the pouring of concrete. For beam and slab construction, bars are placed in a grid pattern and lashed together using hog rings or bar chairs to maintain the cover spacing from the surface. In columns, bars are arranged in a central cage configuration secured using spacers. Mechanized cages speed up construction of columns. By maintaining the designed bar locations and cover, steel reinforces achieve composite action with concrete and improve ductility of structures.
Inspection, Testing and Standards for Steel Round Bars
Rebar quality is evaluated by subjecting samples to various mechanical tests specified by construction codes. Tensile testing determines properties like yield strength, ultimate tensile strength and percentage elongation. Bend tests check their ductility by bending tight radius specimens without fracture. Impact tests are conducted on bars, especially those used in earthquake-prone areas. Chemical analysis using spectrography ascertains if the bars meet the chemical composition standards. Non-destructive tests like magnetic particle inspection and ultrasonic flaw detection are carried out at construction sites to identify any surface cracks or subsurface flaws in reinforcement before placing concrete. Indian reinforcement standards IS 1786 and ASTM A615 cover specifications and testing norms for steel circular bars for concrete reinforcement.
Advantages of Using Steel Round Bars in Construction
Some key benefits of employing steel reinforcement bars in structures include:
- High tensile strength: Rebars help increase the tensile strength of concrete many folds, allowing construction of taller and larger load-bearing structures.
- Ductility: The reinforcement provides composite ductility and prevents brittle kinds of failure in concrete even after cracking develops under loading.
- Longevity: When properly placed and with adequate cover, reinforced concrete proves durable with a design life of 50-100 years.
- Economy: Use of reinforcement yields cost savings compared to non-reinforced concrete sections needed for the same loading conditions.
- Versatility: Steel reinforcement bars can reinforce any shape or size of structural elements - beams, columns, slabs, walls etc. effectively.
- Load redistribution: Even after cracking of concrete cover, rebars continue transmitting stresses and enable redistribution of excess loads to adjacent portions.
- Earthquake resistance: The composite action of reinforcement and concrete enhances their ability to absorb seismic energy through hysteretic damping.
Quality Control in Production and Usage
Proper quality control at all stages, right from the production of steel bars to their construction site usage ensures maximum advantage of reinforcement can be availed from in terms of structure safety, service life and overall economy. The manufacturing facilities adhere to stringent process control as per standards to roll bars within the prescribed chemical composition, strength and dimensional limits. Third party audits independently verify and certify their quality management systems. At sites, pre-casting of bar cages, cover blocks use, and pouring technique influence the long-term bar-concrete bond strength on which reinforced concrete derives its primary benefits. Periodic non-destructive evaluation further substantiates maintenance of bar mechanical properties as designed over the service period.
Conclusion
In summary, the versatile Steel Round Bars have transformed modern construction by enabling larger, taller and stronger concrete structures through efficient utilization of concrete's high compression capacity along with reinforcement's tensile capabilities. When properly manufactured, placed, and maintained, they provide durable and economical solutions for infrastructure and building needs. Advances in alloying and processing also continuously expand their use in more demanding applications and harsh environments.
About Author:
Ravina Pandya, Content Writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemical and materials, etc
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
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