As per IS 456:2000, the minimum grade of concrete for plain concrete and reinforced concrete, respectively, in works exposed directly along the sea coast is:

Try it first: pick an option, then read the explanation.

Correct answer: C. M20 and M30

Minimum Concrete Grade for Sea-Coast Exposure (IS 456:2000)

IS 456:2000 classifies direct sea-coast exposure as a severe exposure condition. The code specifies minimum concrete grades to ensure the structure survives chloride attack and carbonation in this aggressive environment.

IS 456:2000 — Severe (sea coast) exposure:
Plain concrete (PCC) → minimum M20
Reinforced concrete (RCC) → minimum M30

RCC requires a higher grade than PCC because the embedded steel reinforcement is vulnerable to chloride-induced corrosion. A lower permeability (higher grade) concrete provides better protection to the bars.

M20 (PCC) and M30 (RCC) — option C.

Key takeaway

Severe/sea-coast exposure → M20/M30. The RCC grade is one step higher than PCC to protect the steel.

As per IS 456:2000, the minimum grade of concrete for plain concrete and reinforced concrete, respectively, in works exposed directly along the sea coast is:

Minimum Concrete Grade for Sea-Coast Exposure (IS 456:2000)

Key takeaway

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