What is Rebar?

Known as a critical component of concrete construction, rebar provides strength and reinforcement to concrete slabs for a wide range of commercial and residential projects.

Rebar is used widely in the construction industry and is available in different grades and types to provide the right amount of strength and reinforcement. But, what is rebar, exactly?

What is Rebar?

Rebar are steel bars used to improve the tensile strength – or the maximum load a material can support without fracturing while being stretched – of concrete.

Because concrete is strong in compression but very weak in tension, rebar is necessary to compensate for this imbalance and help reinforce the material.

Rebar is made of steel because the elongation of steel due to high temperatures (thermal expansion coefficient) is almost equal to that of concrete.

While all concrete is prone to cracking at some point, rebar and other reinforcing materials can help control where the cracks occur and the extent of the damage.

Rebar Grades

It’s important to know the grade of a steel reinforcement bar, as it shows the amount of tensile strength it has in terms of pounds per square inch (or PSI).

As the grade number increases, the minimum yield strength and minimum tensile strength increases.

For instance, grade 33 rebar is at the low end with a minimum yield strength of 33,000 PSI, making it unsuitable for larger concrete construction projects such as bridges and tunnels.

When shopping for rebar, you can typically find the grade stamped between the lines of the rebar itself.

You will likely notice three printed characters (for instance, E6S):

• The first character (E) refers to the manufacturer
• The second character is for the grade (6 for 60)
• The third character is for the material (S for steel)

Different Types of Rebar

In addition to grades, rebar is available in a variety of types. The most common types of rebar include:

1. Mild Rebar

Mild rebar can be identified by its plain and round shaped surface. Available in a variety of diameters (from 6mm – 50mm), mild rebar can be used to reinforce concrete for:

• Dowels at expansion joints
• Contraction joints in runways and roads
• Column spirals

This rebar is easy to bend without causing damage. It also is the easiest rebar to cut. However, this type of rebar doesn’t bond well to concrete which causes slippage.

2. Deformed Rebar

Unlike mild steel bars, deformed rebar has lugs, ribs, and indentations on the surface of the bar to reduce slippage and help it bond to concrete effectively. If you’re looking for which rebar is used in concrete, this is typically the one.

When comparing deformed rebar to other types, one of the main differences is it boasts higher tensile properties.

Deformed steel reinforcement bars are produced in sections and range in diameter from 6mm – 50mm.

3. Thermo Mechanically Treated Deformed Rebar

These heat treated bars are used in reinforced cement concrete (RCC) work and have a variety of characteristics that make them ideal for these types of jobs, including:

• Superior ductility and malleability
• High yield strength
• Enhanced bonding strength
• High thermal and corrosion resistance
• Earthquake resistance
• No loss in strength at welded joints

4. High Strength Deformed Rebar

These deformed bars are cold twisted with ribs, lugs, projection or deformation on the bars’ surfaces.

Used to reinforce concrete in construction projects, high strength deformed rebar is produced in different sizes or sections ranging in diameter, from 4mm – 50mm.

Characteristics that make HSD rebar stand out include:

• Low Carbon Content: this results in good ductility, welding ability, and strength.
• Optimal Bonding Strength: HSD rebar bonds better to concrete without any slippage.
• Welding Capability: because HSD bars have a low carbon content they can be welded, unlike conventional steel bars.
• High Tensile Strength: this makes HSD bars ideal in construction projects, where a lot of bending is required.
• Multiple Applications: can be used for a variety of applications including bridges, industrial structures, homes, etc.

Other Types of Rebar

Reinforced steel bars can also be categorized by the material used in the manufacturing process. Therese types include:

1. European Rebar

Made of a trace mineral called manganese, European rebar is one of the most affordable rebar types.

However, because this type of rebar bends easily it’s not suitable for extreme weather conditions or geological events like tornadoes, earthquakes, or hurricanes.

2. Carbon Steel Rebar

Commonly referred to as Black Bar due to its color, carbon steel rebar is high in tensile strength and low in cost.

The biggest drawback of carbon steel rebar is the fact that it corrodes which can have a negative impact on the concrete and structure. Concrete projects often need to drill through the rebar because of this.

However, carbon steel rebar can be coated in epoxy to make it 70-1,700 times more corrosion-resistant.

With that said, epoxy coating is extremely delicate, so if/when it becomes damaged the rebar becomes less resistant to corrosion.

3. Galvanized Rebar

While galvanized rebar is only about 40 times more corrosion-resistant than epoxy coated carbon steel rebar, its coating is more difficult to damage.

This makes galvanized rebar more valuable. However, it is much more expensive

4. Glass-Fiber-Reinforced-Polymer

Glass-fiber-reinforced-polymer (or GFRP) is made up of carbon fibre to prevent it from bending.

It’s also extremely resistant to corrosion, but is more expensive than a lot of other rebar types out there.

5. Stainless Steel Rebar

By far the most expensive rebar available – about 8 times the price of epoxy-coated carbon steel bars – stainless steel rebar is suitable for most projects.

With that said, it’s often overkill to use stainless steel rebar in projects unless it absolutely calls for it.

Stainless steel rebar is 1,500 times more corrosion-resistant than black bar and more resistant to damage than any other corrosive-proof rebar types. It can also be bent in the field.

Final Thoughts

So…what is rebar? To recap, rebar is used to reinforce concrete by improving the tensile strength. It’s a crucial part of concrete construction and one that is used for a variety of projects.

From runways and bridges to driveway flooring and basement walls, rebar is necessary to ensure the structural integrity of these concrete construction projects.

Without rebar, concrete slabs can fracture and crumble, which would be a disaster in most situations.