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concrete reinforcing bar (rebar)

In the United States, the size designations of these mild steel bars used to reinforce concrete are set by the ASTM.1 Distributors usually stock rebar in 60 foot lengths.

Most bars are “deformed,” that is, a pattern is rolled onto them which helps the concrete get a grip on the bar. The patterns are not specified. Plain bars are also made, but are used only in special situations in which the bars are expected to slide (for example, crossing expansion joints in highway pavement).

The size designations are based, at least through #8 bar, on the diameter in eighths of an inch of a plain round bar having the same weight per foot as the deformed bar.

Specifications require that the producer roll into the bar:

1. A letter or symbol identifying the mill that produced the bar.

2. The bar size.

3. A symbol indicating the type of steel. for example, means the bar was rolled from a new billet.

4. If the bar is grade 60, a mark indicating it is grade 60. Two styles of marking the grade are used.

In the continuous-line system, grade 60 bars have a line running the length of the bar; grades 40 and 50 do not.
In the number system, the number ”60“ is actually rolled onto the bar, below the mark for the type of steel.
Bar size Weight in pounds per foot nominal diameter in inches (not including the deformations
#3 0.376 0.375, that is, 3/8
#4 0.668 0.500, that is, 4/8
#5 1.043 0.625
#6 1.502 0.750, that is, 6/8
#7 2.044 0.875
#8 2.670 1.000, that is, 8/8
#9 3.400 1.128
#10 4.303 1.270
#11 5.313 1.410
#14 7.650 1.693
#18 13.60 2.257

1. The American Society for Testing and Materials (ASTM) issues a series of specifications for rebar:

A615: Standard Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement. (covers grades 40 and 60)

A616: Standard Specification for Rail-Steel Deformed Bars for Concrete Reinforcement. (Covers grades 50 and 60).

A617: Standard Specification for Axle-Steel Deformed Bars for Concrete Reinforcement. (covers grades 40 and 60)

A706: Standard Specification for Low-Alloy-Steel Deformed Bars for Concrete Reinforcement. (grade 60 only)