Concrete Mix Design MCQ with answer and solution

Concept

Flexural Strength of Concrete

Formula

f_cr = 0.7 × √(f_ck)

Step-by-step solution

Identify the characteristic compressive strength (f_ck), calculate its square root, and multiply by 0.7 to get the flexural strength (f_cr).

Explanation

Concrete pavements are subjected to heavy vehicle loads that cause bending and tensile stresses. Because concrete is much weaker in tension than in compression, the mix design for pavements is primarily based on flexural strength (modulus of rupture) to prevent bending cracks under traffic loads.

Shortcut

Think of a pavement taking the load of bending vehicle tires: pavements bend/flex under load, so pavement concrete mix design is based on **Flexural** strength.

Common mistake

Many students select characteristic compressive strength (Option B) because standard structural concrete design is typically based on compressive strength, overlooking that pavement concrete specifically requires flexural strength to withstand bending stresses caused by traffic loads.