The term deformed steel bars for concrete reinforcement is commonly shortened to rebars. The short form will be used in this section.
Standard rebars are produced in 11 sizes, designated on design drawings and in project specifications by a size number. Since the late 1990s, bar producers have been manufacturing soft-metric rebars for use in both metric and inch-pound construction projects. Soft metric rebars have the same physical features as the corresponding inch-pound bars, i.e., the same nominal diameters and weight per foot (Table 9.4). Soft metric bars are marked with the metric size number and the metric grade of steel.
Table 9.5 shows the bar sizes and strength grades covered by ASTM Specifications A615/A615M and A706/A706M.* The grade number indicates minimum yield strength, MPa [ksi] of the steel. Grade 420 [60] billet-steel rebars, conforming to ASTM A615/A615M, are currently the most widely used type.
Low-alloy steel rebars conforming to the ASTM A706/A706M Specification are intended for applications where controlled tensile properties are essential, for ex- ample, in earthquake-resistant design and construction. The A706/A706M Specification also includes requirements to enhance ductility and bendability. Rebars conforming to A706/A706M are also intended for welding. Weldability is accomplished by the specifications limits or controls on the chemical composition of the steel. Welding of rebars should conform to the requirements of StructuralWelding CodeReinforcing Steel, ANSI/AWS D1.4.
Billet-steel rebars conforming to ASTM A615/A615M are not produced to meet weldability requirements. They may be welded, however, by complying with the requirements in ANSI/AWS D1.4.
Coated rebars, either epoxy-coated or zinc-coated (galvanized), are used where corrosion protection is desired in reinforced concrete structures. The ACI 318 Building Code requires epoxy-coated rebars to conform to ASTM Specifications A775/ A775M or A934/A934M. Zinc-coated (galvanized) rebars are required to conform to ASTM A767/A767M.
ASTM Specification A955M for stainless steel rebars was published in 1996.
Stainless steel rebars are intended for use in highly-corrosive environments, or in buildings which require non-magnetic steel reinforcement.
In 1997, ASTM issued Specification A970/A970M for headed reinforcing bars.
A headed rebar consists of a head fastened or connected to one or both ends of a rebar. The head, which can be a rectangular or round steel plate, is connected to the rebar by welding or threading. Another type of headed rebar has an integrallyforged head. The purpose of the head is to provide end anchorage of the rebar in concrete. Headed rebars can be used advantageously in lieu of bars with standard end hooks thereby relieving congestion of reinforcement and enhancing constructability.
