Which two main categories of reinforcing bars are used in concrete construction?

• A. Deformed bars (ribbed) and plain bars (smooth)
• B. Stainless steel bars and carbon fiber bars
• C. High-strength bars and low-strength bars
• D. Hollow-core bars and solid bars

Answer: (A)

Reinforcing bars are classified by surface texture into two main types: deformed bars with ribs and plain bars without ribs. This distinction matters because how the bar bonds to the surrounding concrete is a key factor in how well the reinforcement can carry tensile forces.

The ribs on deformed bars grip the concrete, creating a strong mechanical interlock. This bond prevents the steel from pulling out and allows the concrete to work together with the steel to resist tension, which is essential for developing the bar’s full strength and the structure’s intended performance.

Plain bars, being smooth, don’t develop as much bond with concrete. They rely more on adhesion and friction, which is weaker, so they’re used only in specific cases where bond isn’t as critical or where other design considerations apply.

So the standard, most commonly used category is deformed (ribbed) bars, with plain (smooth) bars serving limited roles. The other options describe materials or attributes that aren’t the basic surface-bonding distinction.