What is Steel Reinforcement?
Steel reinforcements, often called steel rebars, are integrated with concrete to form reinforced concrete.1 These essential components come in various sizes and types, specifically chosen based on the intended use, anticipated load, and location of the reinforced concrete structural element.2
Why Reinforced Concrete Requires Steel Reinforcement
Fundamentally, concrete exhibits remarkable compression strength but is inherently weak when subjected to tension.3 To enhance the tensile properties of concrete structures, the inclusion of specific sizes and types of steel reinforcement becomes necessary.4 Steel reinforcement, unlike concrete, is renowned for its strength in both tension and compression. The tensile capacity provided by steel reinforcement is crucial for preventing and minimizing concrete cracks under tensional loading.5
A key advantage lies in the nearly identical coefficient of thermal expansion between steel reinforcement and concrete.6 This shared property ensures that both materials expand and contract similarly during temperature fluctuations, subjecting the concrete to minimal stress and preventing issues like cracking due to differential movement.7
Furthermore, the unique patterned surface surrounding rebar ensures excellent bonding with the concrete, facilitating a cohesive and robust composite material.
Types of Steel Reinforcement
The steel reinforcement commonly employed in concrete construction primarily falls into four categories:
- Hot Rolled Deformed Steel Bars: These are the most frequently used steel reinforcement in reinforced concrete structures. As the name suggests, the hot rolling process creates specific deformations (ribs) on the bar’s surface. These ribs are vital for forming a strong bond with the concrete.8 Hot rolled deformed bars typically exhibit a yield strength of 60,000 psi.9 They are generally specified as high tensile steel and are denoted as “T” for 460 N/mm² or “Y” for 410 N/mm².
- Cold Worked Steel Bars: A cold worked reinforcement bar is produced by taking hot rolled steel bars and subjecting them to a cold working process, which involves twisting and drawing the bars at room temperature.10 Compared to hot rolled bars, cold worked steel bars have less ductility because they do not undergo plastic yield during processing.11
- Mild Steel Plain Bars: These reinforcement bars are characterized by their smooth, plain surface, lacking the ribs found on deformed bars.12 They are typically used for smaller projects where economy is a primary concern. Mild steel plain bars have a lower tensile yield strength of 40,000 psi. They are generally specified as mild tensile steel and are denoted as “R” for 250 N/mm².13
- Prestressing Steel Bars: Prestressing steel reinforcement is utilized in the form of strands or tendons.14 These involve multiple strands (often 2, 3, or 7 individual wires) integrated into concrete to achieve the prestressing action.15 The wires themselves are cold-formed and possess an exceptionally high tensile strength, ranging from 250,000 to 270,000 psi.16 This immense strength is crucial for effectively prestressing the concrete.
Advantages of Steel Reinforcement
Steel reinforcement is a preferred choice over other reinforcing materials due to its distinct advantages:
- Compatibility with Concrete: When fresh concrete is placed into formwork already prepared with reinforcement, the steel reinforcement does not float. This means steel reinforcement doesn’t require special tying to the formwork to maintain its position during concrete placement.
- Robustness: Steel bars are inherently robust, possessing the ability to withstand the rigors and wear and tear encountered during various construction activities.17
- Bend Property: Once manufactured to standard sizes, steel bars can be readily bent to meet specific design requirements. This allows for the easy delivery of pre-fabricated steel bars to the construction site.
- Recycling Property: Steel reinforcement left over after a structure’s service life can be efficiently recycled and repurposed for new construction projects.18
- Easy Availability: Given the widespread nature of steel suppliers and manufacturers, steel reinforcement is readily available in most regions.19
Disadvantages of Steel Reinforcement
Despite its numerous benefits, steel reinforcement also presents certain disadvantages:
- Reactive Nature: In concrete structures where the protective cover is thin and exposed to external moisture and salt, the reinforcement can react and begin to corrode. This corrosion can significantly reduce the concrete’s strength, potentially leading to structural failure.20
- Expensive: The cost of steel reinforcement is relatively high, which can notably increase overall construction expenses.
- Melts at High Temperature: Steel reinforcement can melt at elevated temperatures. This characteristic is why rebars are typically tied together rather than welded in many applications, to mitigate potential structural compromise in fire scenarios.
Phoenix Reinforcing is a dedicated concrete reinforcing business located in Queensland, ready to assist with your reinforcing and building needs. We specialize in reinforcing sales, scheduling, estimating decorative concrete products, and more. Contact us today to learn how we can help you!