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Increased cover specifications in IS 456: 2000 - Crack-width implications in RC slabs
Archana Gouthaman,
Published in
Volume: 75
Issue: 9
Pages: 581 - 586
The incresead cover specifications in the recently-revised IS 456 will serve the desired objective of enhancing durability, only if the cracking of the cover concrete (under tension) is effectively controlled. Increased cover in flexural members such as RC slabs will lead to increased crack-width, which in turn, will adversely affect durability by permitting ingress of moisture and chemcial attack. The need for the designer to necessarily check for the limit state of serviceability (cracking) has not been sufficiently emphasised in the revised code. Instead, it is mentioned that such a check need not be carried out if the prescribed detailing (bar spacing) is followed. This paper attempts to establish that this assumption is generally not satisfied in RC slabs. Crack-width control is most effectively achieved by reducing the tensile stress in the steel and by minimising bar spacing. Results of a parametric study bring out the difficulties in maintaining the crack-width below 0.3 mm when large cover is provided; such cases may necessitate an incresed in the slab thickness.
About the journal
JournalIndian Concrete Journal
Open AccessNo
Concepts (7)
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    Chemical attack
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    Crack initiation
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    Structural members
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    Tensile stress
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    Reinforced concrete