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. Two general systems of bar branding are used. Both systems serve the basic purpose of identifying the marker size, the type of steel, and the 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 3-8 shows the two-grade marking system.
The lower strength reinforcing bars show only three marks: an initial representing the producing mill, the bar size, and the type of steel. The high strength reinforcing bars use either the continuous line system or the number system to show grade marks. [n 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 3-8. 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 3-9. The sheet steel has been sheared in parallel lines and then pulled out or expanded to form a diamond shape between each parallel cut. Another type is square, rather than diamond shaped, as shown in view B, figure 3-9. Expanded metal is customarily used during plastering operations and light reinforcing concrete construction, such as sidewalks, and small
Figure 3-8. - American standard reinforcing steel bar marks.
concrete pads, that do not have to bear substantial weight, such as transformer and air-conditioner pads.
Welded wire fabric is fabricated from a series of wires arranged at right angles to each other and electrically welded at all intersections. Welded wire 3-19Continue Reading