Rebar is a shortened term used to described steel reinforcing bar. The product is used as a skeleton when concrete pillars, walls and foundations are poured during construction. Rebar gives the concrete strength as the stone aggregate hardens around the steel framework. Like steel used in other industries, rebar is manufactured in different sizes and grades of steel. Based on its grade, some rebar used in construction can be welded, while some can not.
According to The American Welding Society publication "AWS D 1.4," low alloy steel rebar can be welded. The steel-to-carbon ratio of this grade steel is suitable for welding, and the welds can be expected to hold together under load, and after they are sealed in concrete. This is the only rebar ready to weld without special consideration given for a particular use and setting. W grade, low-alloy steel, specifically A706 steel, can be welded when used in steel fabrication.
The formula of steel is the determining factor for whether or not steel can be welded. As the carbon content of steel rises, and in high strength alloy steels, the metal becomes more brittle. This is an advantage for the strength the steel provides to the concrete. However, it is a disadvantage when considering welding the material. The more brittle the steel, the more likely the weld will fracture under stress. Imagine trying to bend a piece of soft taffy candy as opposed to bending taffy just out of the freezer. The soft material bends, while the brittle material fractures. High-strength and alloy steels may not be welded because they're more likely to fracture under load.
How Rebar Is Used
Rebar is used to reinforce concrete. The stone aggregate has high strength properties, but is physically brittle. By pouring concrete around a reinforced steel cage, much like the human body is formed via muscles attached to bone skeleton, the steel creates a backbone, a structure which adds strength and flexibility to the concrete. For example; concrete I-beams used for the main support ribs on highway bridges are poured on a steel rebar cage. Alone, the concrete would snap and break under load. Because of the rebar, the inflexible concrete takes on some of the flexing characteristics of steel, and performs well.
How Rebar Is Connected
When rebar cannot be welded, the pieces of the steel cages are mechanically tied together with 16-gauge wire. The wire is wrapped around every joint, and the pieces tied together. The advantage of wire-tied rebar is that complicated cages can be built on the construction site. Workers can assemble the cages, and tie off the individual pieces of rebar based on the needs of the individual project. On the job site, tying rebar together into cages can be completed more quickly than individually welding each joint.