Table 7-3. - Comparison of U.S. Customary and Metric Rebar
|U.S. Standard Bar||Metric Bar||Metric Bar is:|
|Bar Size||Area Sq. Inches||Bar Size||Area Sq. Inches|
|#14||2.25||45m||2.33||3 .5% larger|
|#18||4.00||55m||3.88||3 .0% smaller|
*NOTE: % Difference is based upon area of rebar in square inches.
Reinforcing bars are hot-rolled from a variety of steels in several different strength grades. Most reinforcing bars are rolled from new steel billets, but some are rolled from used railroad-car axles or railroad rails that have been cut into rollable shapes. An assortment of strengths are available.
The American Society for Testing Materials (ASTM) has established a standard branding for deformed reinforcing bars. There are two general systems of bar branding. Both systems serve the basic purpose of identifying the marker size, type of steel, and grade of each bar. In both systems an identity mark denoting the type of steel used is branded on every bar by engraving the final roll used to produce the bars so as to leave raised symbols between the deformations. The manufacturer's identity mark that signifies the mill that rolled the bar is usually a single letter or, in some cases, a symbol. The bar size follows the manufacturer's mark and is followed by a symbol indicating new billet steel (-N-), rolled rail steel (-I-), or rolled axle steel (-A-). Figure 7-2 shows the two-grade marking system.
The lower strength reinforcing bars show only three marks: an initial representing the producing mill, bar size, and type of steel. The high strength reinforcing bars use either the continuous line system or the number system to show grade marks. In the line system, one continuous line is rolled into the 60,000 psi bars, and two continuous lines are rolled into the 75,000 psi bars. The lines must run at least five deformation spaces, as shown in figure 7-2. In the number system, a "60" is rolled into the bar following the steel type of mark to denote 60,000 psi bars, and a "75" is rolled into the 75,000 psi bars.
Expanded metal or wire mesh is also used for reinforcing concrete. Expanded metal is made by partly shearing a sheet of steel, as shown in view A figure 7-3. The sheet steel has been sheared in parallelContinue Reading