Reinforcing steel bars are used to help concrete withstand tension forces. Concrete by nature is sufficiently strong to compression forces, although tension forces can crack concrete. Deformed rebars on reinforcing steel were made a standard requirement since 1968, however, plain rebars are also used in situations where the reinforcing steel is expected to slide as usually installed in highway pavement and in segmental bridges.
The deformed pattern on a rebar will help the concrete to adhere to the reinforcing steel surface. The pattern on a deformed bar is not specified, however, the spacing, and the height of the ‘bumps’ is regulated.
Rebar: Reinforcing Steel Bar Specifications
Reinforcing bars are hot-rolled using different steel materials. Most rebars are rolled from new steel billets, while others are rolled from steel debris or railroad rails. Rebars are required to contain some sort of identification that could be used to identify the mill that produced the reinforcing steel bar.
The ASTM (American Society for Testing and Materials) has created a standard identification ruling that all rebars must comply with:
- The Number identifying the bar size.
- Type of steel symbol.for example, means the bar was rolled from a new billet, “W” for weldable steel (ASTM A-706), A for Axle (M 322 / ASTM 966) and so on.
- The rebar grade identification, either 60 or 75, or metric 420 or 520. This grade indicates the rebar yield strength.
- A symbol identifying the manufacturer that rolled the bar. It is usually a single letter or a plain symbol.
Lower strength reinforcing steel bars has only three marks that identify the mill that produced the bar, the rebar size and the type of steel used. High strength reinforcing steel uses a continuous line system to show steel grade.
If the rebar contains two lines it indicates that the rebar was rolled into the 75,000 psi bars, however, when a single line is present, it represents a 60,000 psi bar.
5 Rebar Types
- Welded Wire Fabric – Welded wire fabric is made from a series of steel wires arranged at right angles and electrically welded at all steel wires crossings. Welded wire fabric, also known as WWF, can be used in slab-on-ground slabs, where the ground has been well compacted. A heavier fabrication of welded wire fabric can be used in walls and structural floor slabs. This is commonly used in road pavements, box culverts and drainage structures, and small concrete canals.
- Sheet-Metal Reinforcing Bars – Sheet-metal reinforcement is commonly used in floor slabs, stairs and roof construction. Sheet-metal reinforcing is composed of annealed sheet steel pieces bent into corrugations about 1/16 inch depth, with holes punched at regular spacing.
- Stainless Steel Rebars – Stainless steel can be used as an alternative reinforcing steel bar with carbon steel reinforcement. Using stainless steel reinforcing bars will not create galvanic corrosion, and can be a cost-effective solution in areas subject to corrosion problems, or where repair is difficult and expensive. They will cost at least 8 times more than epoxy-coated rebars.
- Expanded Metal or Wire Mesh – Expanded metal or wire mesh reinforcement is also another good reinforcement product for concrete. Expanded metal is made by shearing a sheet of steel into parallel lines and the expanded to form a diamond shape or square shape between each cut. Expanded metal is commonly used as reinforcement in areas where a considerable thickness of plaster is required, or to reinforced light concrete construction. Wire mesh reinforcement can be used on sidewalks, small concrete pads or walkable surfaces that do not receive high live nor load charges.
- Epoxy-Coated Rebars – Epoxy-coated rebars are expensive and used in areas that will be either in contact with salt water or where the corrosion problem is imminent. The only problem is that sometimes the coating can be very delicate and this, so make sure to order those bars from a reputable supplier.
Rebar Prices and Cost
The cost of rebar can be estimated on a per foot basis or per ton. A good number that you can use is $0.85 per foot and higher depending on the size and type of rebar. When buying per ton, you can get about 150 rebars #4 measuring 20 feet long and 96 rebars and it would be the best way of purchasing rebars as it will get you the best pricing. The cost of steel varies from month to month and even daily so make sure to lock in the price ahead of time for better pricing. The cost of one ton of steel can be around $650 so be sure to check with your supplier for a more accurate price.
Content retrieved from: https://www.thebalance.com/types-of-rebars-844455.