Which best describes the standard type of reinforcing bar?

• A. Deformed bar
• B. Plain bar
• C. Spiral bar
• D. Welded bar

Answer: (A)

Reinforcing bar is designed to bond with concrete, and the surface finish of the bar is crucial for that bond. Deformed bars have ridges or indentations along their length, which create a mechanical interlock with the surrounding concrete. This rough surface increases bond strength, helps transfer tensile stresses from the steel to the concrete, and allows the steel to develop its full strength without slipping. Plain bars are smooth, so they rely mostly on adhesion and friction, which is much weaker and leads to slipping under load. Spiral bars and welded-bar terms describe other specialized reinforcement uses, not the standard reinforcing bar found in most reinforced concrete members. So the best choice is the deformed bar, because its ribbed surface provides the reliable bond needed for typical reinforcement.