Which feature distinguishes deformed reinforcing bars from plain reinforcing bars?

• A. Non-metallic
• B. They are always epoxy-coated
• C. They are used only in decorative work
• D. Deformed bars have ribbed surfaces that improve bond with concrete; plain bars are smooth

Answer: (D)

The important idea is how the bar’s surface texture affects bonding with concrete. Deformed reinforcing bars have ribbed or deformed surfaces that create mechanical interlock with the surrounding concrete as it cures. This ribbing increases bond strength and slip resistance, so the bar can effectively transfer tensile forces into the concrete. Plain bars, by contrast, are smooth and rely mainly on adhesion and friction, which provide much less bond strength.

That’s why this feature distinguishes them: the ribbed surfaces on deformed bars improve the bond with concrete, while plain bars are smooth and offer weaker bonding. The other statements aren’t defining characteristics: reinforcing bars are metallic, not non-metallic; coatings like epoxy aren’t required for all bars; and they’re not limited to decorative work.