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 diamond-shaped 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 A305-49 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 A305-49.
– 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.
– Corrosion-resistant materials like epoxy-coated, galvanized, or stainless steel rebars are used in saltwater or marine applications.
– Epoxy-coated rebar provides better corrosion resistance than uncoated rebar.
– Damage to epoxy-coated rebar reduces its long-term 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 cross-sectional area of a bar is calculated using the formula (bar size/9)^2.
– Bar sizes larger than #8 follow the 1/8-inch 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.
– Fiber-reinforced plastic (FRP) rebar is used in high-corrosion 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 non-magnetic.

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.https://en.wikipedia.org/wiki/Rebar