Rebar

Definition, Purpose, and History of Rebar Rebar is short for reinforcing bar, used to strengthen and support concrete and masonry structures. It is made of steel and increases the tensile strength of the structure. Rebar has a ribbed surface to enhance bonding with concrete and prevent slippage. Carbon steel is the most common type of rebar, but other options like stainless steel and composite bars are available. Coatings like zinc or epoxy resin can be applied to protect against corrosion. Rebar has been used since ancient times, with iron or wooden rods in arch construction. In the 19th century, steel bars were embedded in concrete, leading to the development of modern reinforced concrete. Notable figures in the invention and popularization of reinforced concrete include Joseph Monier and Ernest L. Ransome. Twisted iron rebar was initially met with skepticism but was used in the first reinforced concrete bridge in the United States. Different reinforcing systems, such as the mushroom system and diamondshaped rebar, were experimented with but faced criticism and were eventually replaced. Use and Benefits of Rebar Rebar is used in concrete to provide tensile strength, compensating for its weakness in tension. Primary reinforcement ensures the overall resistance needed to support design loads. Secondary reinforcement, also known as distribution or thermal reinforcement, limits cracking and resists stresses caused by temperature changes and shrinkage. Rebar can also be embedded in masonry walls for added strength and stability. Rebar significantly increases the tensile strength of concrete structures, making them more durable and resistant to cracking. It enhances the structural integrity and stability of buildings, bridges, and other reinforced concrete elements. The use of rebar allows for the construction of larger and more complex structures. Different types of rebar, such as stainless steel or composite bars, offer specific performance advantages in certain construction projects. Coatings like zinc or epoxy resin protect rebar from corrosion, extending its lifespan in harsh environments. Standards and Specifications for Rebar Deformations on steel bar reinforcement were standardized in the US construction industry around 1950. ASTM A30549 established the requirements for deformations, including rib height and spacing. Current specifications for steel bar reinforcing, such as ASTM A615 and ASTM A706, maintain the same deformation requirements as ASTM A30549. These standards ensure the quality and performance of rebar in reinforced concrete structures. Compliance with these specifications is essential for the safety and longevity of the construction projects. Physical Characteristics, Corrosion Prevention, and Sizes of Rebar Steel has a thermal expansion coefficient similar to modern concrete. Rebar can be pulled out of concrete under high stresses, leading to collapse. Rebar is deeply embedded or bent and hooked to prevent failure. Unfinished tempered steel rebar is susceptible to rusting. Concrete cover must provide a pH value higher than 12 to avoid corrosion. Uncoated steel rebars can be prone to rusting. Corrosionresistant materials like epoxycoated, galvanized, or stainless steel rebars are used in saltwater or marine applications. Epoxycoated rebar provides better corrosion resistance than uncoated rebar. Damage to epoxycoated rebar reduces its longterm corrosion resistance. Stainless steel rebar with low magnetic permeability is used to avoid magnetic interference. US/Imperial bar sizes are given in units of 1/8 inch. The crosssectional area of a bar is calculated using the formula (bar size/9)^2. Bar sizes larger than #8 follow the 1/8inch rule and skip certain sizes due to historical convention. Sizes smaller than #3 are not recognized as standard sizes. US/Imperial bar sizes can be converted to metric sizes, but it may result in physically different sized bars. Fiberreinforced plastic (FRP) rebar is used in highcorrosion environments. FRP rebar is available in various forms like spirals, rods, and meshes. Most commercially available FRP rebar is made from unidirectional fibers set in a thermoset polymer resin. Glass fiber types of FRP rebar have low electrical conductivity and are nonmagnetic. Rebar Sizes in Different Countries Metric bar designations represent the nominal bar diameter in millimeters. Preferred bar sizes in Europe comply with Table 6 of the standard EN 10080. Various national standards still remain in force, such as BS 4449 in the United Kingdom. Reinforcement for concrete construction in Australia follows the requirements of Australian Standards AS3600 and AS/NZS4671. Reinforcement for concrete construction in New Zealand complies with the requirements of AS/NZS4671. Rebars in India are available in different grades such as FE 415, FE 415D, FE 415S, FE 500, FE 500D, FE 500S, FE 550, FE 550D, and FE 600. Very large format rebar sizes are available from specialty manufacturers. Jumbo bars are commonly used as anchor rods for large structures in the tower and sign industries. Fully threaded rebar with coarse threads is produced to satisfy rebar deformation standards and allow for custom nuts and couplers.