The 'crack width' in RC flexural members is controlled by IS 456 by:
Choose the correct answer
Only by using high-grade concrete (fck > 50 MPa)
Bar size, bar spacing limits, and adequate cover — IS 456: max crack width 0.3 mm moderate; 0.2 mm severe exposure
Only by pre-stressing every member
By using only compression reinforcement
Correct Answer
B. Bar size, bar spacing limits, and adequate cover — IS 456: max crack width 0.3 mm moderate; 0.2 mm severe exposure
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IS 456 Cl. 35.3 and Annex F: crack width limit (design surface crack width) ≤ 0.3 mm (moderate) or 0.2 mm (severe/very severe). Control measures: (1) Limit bar diameter; (2) Limit bar spacing (IS 456 Cl. 26.3.3: max spacing 300 mm); (3) Adequate cover; (4) Distributed steel. Formula: wcr = 3×acr×εm / (1 + 2×(acr−cmin)/(h−x)) where εm = mean strain. Practical: limit (fs/fy)×(bar dia/cover) ratio.
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