The 'fire resistance' of an RC member depends primarily on:
Choose the correct answer
Only the grade of concrete (fck value)
Cover (delays heat to steel), section size (thermal mass), and concrete/aggregate type — IS 456 Annex A fire ratings
Only the shape of the section (circular vs rectangular)
Only the yield strength of steel bars
Correct Answer
B. Cover (delays heat to steel), section size (thermal mass), and concrete/aggregate type — IS 456 Annex A fire ratings
Why is this the answer?
Fire resistance (IS 456 Annex A; IS 3809): (1) Cover to reinforcement — deeper cover delays heat reaching steel; (2) Concrete type (NWC, LWC — lightweight better insulator); (3) Section size — larger section = longer time before temperature rise; (4) Aggregate type (calcareous better, siliceous spall). Fire rating: 0.5hr, 1hr, 1.5hr, 2hr, 3hr, 4hr. Cover requirement: 20mm (0.5hr), 40mm (2hr), 50mm (4hr). Exposed columns: larger minimum dimension required.
Related RCC MCQs
More solved RCC questions for AE/JE Civil Engineering exams.
- The 'ductility' of RC structures is improved under earthquake loading by:
- For a circular RC water tank with rigid base, the hoop tension is maximum at:
- The 'end block' in a post-tensioned member is specially designed for:
- A 'shear wall' in a multi-storey RC building acts as:
- The 'minimum clear cover' for reinforcement in a RCC beam in severe exposure (IS 456) is:
- The 'torsion' in RC beams is resisted by:
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