What is the difference between plain concrete and reinforced concrete?

• A. Plain concrete relies on cement paste and aggregate for strength; reinforced concrete uses steel to carry tensile stresses
• B. Reinforced concrete uses steel reinforcement; plain uses cement
• C. Plain is stronger in tension
• D. Reinforced concrete cannot be used in foundations

Answer: (A)

The key idea is how each type handles tensile forces. Plain concrete performs well in compression but is weak in tension, so it cracks when pulled or bent. Reinforced concrete combines concrete with steel reinforcement that takes up the tensile stresses the concrete can’t resist, letting the whole member carry bending, shear, and other loads more effectively. The cement paste and aggregate provide the compressive strength, while the steel provides the ductile tensile strength, giving reinforced concrete its characteristic strength and toughness. That’s why the best description is that plain concrete relies on cement paste and aggregate for strength, and reinforced concrete uses steel to carry tensile stresses. The other notions either misstate concrete’s behavior in tension or are inaccurate about common use (for example, plain concrete isn’t stronger in tension, and reinforced concrete is commonly used in foundations).