What is difference between clear cover nominal cover and effective cover in RCC
● introduction :- in this article discuss about what is difference between clear cover nominal cover and effective cover in RCC structure. Concrete cover is provided in all structure member like different types of footing column beam and slab. Concrete cover is provided for long lasting life of concrete and keep RCC structure free from corrosion and rust formation.
What is clear cover in concrete
Clear cover is the least and minimum distance between outer face of concrete fibre and the outer face of main reinforcement with link excluding thickness of Plaster and finishing of concrete. Mostly cover is described as clear cover or minimum concrete cover generally speaking at construction site.
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How to define nominal concrete cover
In simple word least and minimum distance between outer face of concrete fibre to the main reinforcement inserted inside in construction structure. According to IS code 456 -2000 clause 26.4.1 nominal cover can be defined as is the design depth of concrete cover to all Steel including link. So nominal concrete cover is also known as clear cover
How to defined effective cover
Effective concrete cover is least and minimum distance between outer face of concrete fibre to the half dia of main reinforcement which is inserted inside construction structure.
So effective cover is sum of clear concrete cover and half dia of main reinforcement.
Effective cover = nominal cover + half dia of reinforcement
What is importance of clear cover of concrete
1) clear cover of concrete provide and maintain long lasting life of concrete
2) clear cover of concrete keep reinforcement free from corrosion and rust formation and prevent from damaging due to moisture condition in environment and in soil
3) outer face of concrete fibre is thermal insulator and protect reinforcement to sheild it
4) it provides adequate embedding to reinforcement bar to fasilitate them to be stressed without losing grip
5) clear cover of concrete prevent reinforcement from environmental condition moisture and soil
6) thickness or size of clear cover depends on the environmental circumstances and type of a structure member.
Clear cover of different structure member
1) Beam :- size of clear cover should ranging between 25 mm to 40 mm.25 mm is taken in presence of dry climatic environment and 35 mm to 40 mm should be taken in presence of wet climatic environment or see location.
2) Column :- the size of clear cover should ranging between 40mm to 50mm. 40 mm is good for dry weather condition and 50 mm for wet moist weather condition.
3) slab :- the size of clear cover for slab should ranging between 20mm to 30 mm
4) footing :- the size of clear cover for footing should be 60 mm to 75 mm
Why the size of clear cover for footing is greater than other structure member
As we know that Earth excavation done for footing beneath the soil, in foundation footing there is a sand filling ,brick soling layer, PCC layer rcc layer which is coming direct contact with moisture or water present in soil, moisture present in soil wants to damaging concrete fibre and rusting of reinforcement which is inserted inside concrete fibre.
To prevent from rusting and corrosion of reinforcement in soil footing size of clear cover is provided is greater than other structural member like beam column and slab.