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Sizes and grades U.S. sizes Imperial bar designations represent the bar diameter in fractions of 1⁄8 inch, such that #8 = 8⁄8 inch = 1 inch diameter. Area = (bar size/9)2 such that area of #8 = (8/9)2 = 0.79 in2. This applies to #8 bars and smaller. Larger bars have a slightly larger diameter than the one computed using the 1⁄8 inch convention.
Canadian sizes Metric bar designations represent the nominal bar diameter in millimeters, rounded to the nearest 5 mm.
European sizes Metric bar designations represent the nominal bar diameter in millimetres. Bars in Europe will be specified to comply with the standard EN 10080 (awaiting introduction as of early 2007), although various national standards still remain in force (e.g. BS 4449 in the United Kingdom).
Grades Rebar is available in different grades and specifications that vary in yield strength , ultimate tensile strength , chemical composition , and percentage of elongation . The grade designation is equal to the minimum yield strength of the bar in ksi (1000 psi) for example grade 60 rebar has a minimum yield strength of 60 ksi. Rebar is typically manufactured in grades 40, 60, and 75. Common ASTM specification are:
ASTM marking designations are:
Historically in Europe, rebar is composed of mild steel material with a yield strength of approximately 250 N/mm². Modern rebar is composed of high-yield steel, with a yield strength more typically 500 N/mm². Rebar can be supplied with various grades of ductility , with the more ductile steel capable of absorbing considerably greater energy when deformed - this can be of use in design to resist the forces from earthquakes for example.
Placing rebar Rebar cages are fabricated either on or off the project site commonly with the help of hydraulic benders and shears, however for small or custom work a tool known as a Hickey - or hand rebar bender, is sufficient. The rebars are placed by rodbusters or concrete reinforcing ironworkers with bar supports separating the rebar from the concrete forms to establish concrete cover and ensure that proper embedment is achieved. The rebars in the cages are connected by welding or tying wires. For epoxy coated or galvanized rebars only the latter is possible. Welding The American Welding Society (AWS) D 1.4 sets out the practices for welding rebar in the U.S. Without special consideration the only rebar that is ready to weld is W grade (Low-alloy — A706). In the US, most rebar is not suitable for welding. ASTM A 616 & ASTM A 617 reinforcing are re-rolled rail steel & re-rolled rail axle steel with uncontrolled chemistry, phosphorus & carbon content. To weld rebar you must obtain a mill statement that the reinforcing is suitable for welding. Welding can reduce the fatigue life of the rebar, and as a result rebar cages are normally tied together with wire. Besides fatigue concerns welding rebar has become less common in developed countries due to the high labor costs of certified welders. Steel for prestressed concrete may absolutely not be welded. Couplers When welding or wire-tying rebar is impractical or uneconomical a mechanical connection or rebar coupler can be used to connect two or more bars together. These couplers are popular in precast concrete construction at the joints between members and to reduce rebar congestion in highly reinforced areas. A full mechanical connection is achieved when the bars connected develop in tension or compression a minimum of 125% of the yield strength of the bar. Safety To prevent workers and / or pedestrians from accidentally impaling themselves, the protruding ends of steel rebar are often bent over or covered with special steel-reinforced plastic "plate" caps. "Mushroom" caps may provide protection from scratches and other minor injuries, but provide little to no protection from impalement. Designations For clarity, reinforcement is usually tabulated in a "reinforcement schedule" on construction drawings. This eliminates ambiguity in the various notations used in different parts of the world. The following list provides examples of the different notations used in the architectural, engineering, and construction industry.
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