The most common use of steel rebar is reinforcing concrete. However, rebar can also be used in ornamental applications. Those planning to use rebar for ornamental purposes don't have to worry much about grades. Contractors purchasing construction rebar are a different story.
Anyone planning to use rebar in concrete needs to know that there are many kinds of steel used to produce rebar, and each of them is a little different. This article will offer a comprehensive overview of steel rebar types, grades, sizes, and more.
What Is Rebar?
Standard rebar is made from recycled carbon steel. However, this material isn't ideal for all applications. That's why manufacturers also produce low-alloy, stainless, and rail or axle steel rebar and low carbon chromium.
Carbon Steel Rebar
Carbon steel is the most common material used to make rebar. Unfortunately, the production of carbon steel rebar isn't as well-regulated as some manufacturing processes. Manufacturers must ensure that their products meet minimum yield strength requirements across their entire lengths but do not have to meet consistency standards.
Carbon steel rebar is one of the most common forms of construction rebar because it is used in concrete stabilization. More specifically, it's common to see carbon steel rebar in residential and small commercial construction. It provides sufficient strength for this application and its low cost is a big selling point for many contractors.
Low-Alloy Steel Rebar
What sets low-alloy steel rebar apart from its carbon steel alternative is the fact that it is weldable. Otherwise, it is nearly indistinguishable from carbon steel.
Galvanized Steel Rebar
Galvanized steel rebar is coated with zinc using cold-plating, hot-plating, or electroplating. The zinc coating makes it corrosion-resistant, which can be an appealing design feature in areas that see a lot of rain.
Even when concrete is poured correctly, it still has tiny fractures. Water enters these fractures and if it reaches untreated rebar, it causes the metal to rust, causing swelling and expansion that can crack the concrete in a process known as oxide jacking.
Rebar grades refer to the material's minimum tensile strength. They're measured in pounds per square inch. The lowest-grade rebar is grade 33, but few contractors use this kind of low-quality product.
Grade 40 Rebar
Construction rebar starts out at grade 40. Grade 40 has a minimum tensile strength of 60,000 PSI. Its minimum yield strength is 40,000 PSI. It's used for low- to medium-duty concrete reinforcing applications.
Grade 60 Rebar
Grade 60 rebar is used for medium- to heavy-duty concrete reinforcement applications. It boasts a minimum tensile strength of 90,000 PSI and minimum yield strength of 60,000 PSI. It's common to find grade 60 rebar in bridges, skyscrapers, and other engineering applications.
Contractors and engineers can purchase rebar in almost any length, though most rebar is measured in 10" increments. To get the right products, they'll also need to understand how manufacturers measure the rebar's diameter.
In the US, rebar is measured in imperial bar sizes. The system is a bit complicated in that bar sizes #2-#8 are measured in ⅛-inch units, while bar sizes larger than #8 do not follow this rule.
Most manufacturers also follow historical conventions and skip bar sizes #12-13 and #15-17. The earliest concrete rebar could only be manufactured in circular sections if they measured 1" or less in diameter. That's no longer the case, but measurement standards have not changed to reflect that fact.
Don't care about the convoluted history of Imperial measurements? Here's a handy rebar sizing guide that will be more helpful:
Understanding Rebar Designations
Some manufacturers stamp their rebar with a series of letters and numbers. They contain all the information contractors need to make informed purchase and use decisions. The designations can be broken up into four sections based on what they indicate about the rebar.
1. Point of Origin
The first character in the designation should be a letter. That letter indicates the rebar's point of origin, or the metal manufacturing facility where it was made.
2. Rebar Size
The second character should be a number. It designates the rebar's size. Just divide the number on the rebar by eight to get the size in inches.
3. Type of Steel
The third character should be a letter or a set of two letters. It indicates what type of steel was used to make the rebar. Here's what each of the standard letters means along with their ASTM standard designations:
Not all these forms of rebar are used in construction. S, W, and SS designations are most common.
4. Minimum Yield Strength
This number is not always included on rebar designations. If there is no minimum yield strength noted, assume the rebar is grade 40. Otherwise, divide the number by 1,000 to get the product's yield strength in pounds per square inch.
A Final Tip for Choosing Rebar Products
Contractors, engineers, architects, and interested consumers should now have all the information they need to make informed decisions about purchasing rebar. If all else fails, though, it's fine to ask a steel supplier like Hamill Metals for advice before making a purchase.
Tell a customer service representative the rebar's intended application, and any other available details and ask for professional advice. It's always better to ask a professional than purchase the wrong product for the job