Clear cover for slab, beam, column, staircase and footing, hi guys in this article we know about clear cover of Foundation footing, raft Foundation top,Raft Foundation bottom, strap beam, grade slab, column, beam, slab, flat slab, staircase,shear wall, retaining wall and lintel.
Clear cover is 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.
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1)what is concrete and its types and properties
2) concrete quantity calculation for staircase and its formula
What is clear cover of concrete?
Regarding this, “what is clear cover?” 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.
What is nominal concrete cover?
Regarding this, “what is nominal concrete cover?”, Nominal concrete cover is define in simple word as least and minimum distance between outer face of concrete fibre to the main reinforcement inserted inside in construction structure.
Define nominal cover according to IS code
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.
What is importance of clear cover of concrete?
Regarding this, “what is importance of clear cover of concrete?”, Function and importance of clear cover of concrete are following:- 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 facilitate them to be stressed without losing grip, 5) clear cover of concrete prevent reinforcement from environmental condition moisture and soil and 6) thickness or size of clear cover depends on the environmental circumstances and type of a structure member.
Concrete cover specifications as per ACI Code
Commonly the thickness of concrete cover is specified based on the type of reinforced concrete structure and the environment in which structure in constructed.
Concrete cover specification according to ACI code the American code Institute (ACI – 318 – 11) provides the minimum concrete cover thickness for different structure of reinforced concrete such as slab, beam, column, wall, and Joists. ACI Code provides the cover size according to taking consideration about condition such as corrosive environment, fire protection and future extension.
The ACI code is specified that size of concrete cover for Reinforced concrete structure which subjected to remain in seawater should be at least 50mm (2-inch).
Cover for footing/ foundation:- The ACI Code specified that the size of concrete cover for footing/ foundation should be at least 75 mm. Foundation concrete structure cast against permanently in contact with ground.
Cover for column:-The ACI Code specified that the size of concrete cover for column should be at least 50mm in case of higher size of rebar used and 40 mm in case of lower size rebar. Column is the concrete structure in contact with ground or water.
Cover for slab:– The ACI code specified that the size of concrete cover for slab should be at least 20mm in case of lower size rebar used and 40mm in case of higher size rebar. The concrete structure not exposed to weather or ground such as slab, wall and joist.
Cover for beam:- The ACI code specified that the size of concrete cover for beam should be at least 40mm (3/2- inch). Beam is the concrete structure not exposed to weather or ground.
Size of beam cover should be at least 25mm (1-inch) if reinforcement bar is not greater than 12mm and 40mm (1.5-inch) if bar is greater than 12mm. Cover for a beam is the distance between the top surface of the concrete beam and the top surface of the reinforcement.
Size of column cover should be at least 25mm (1-inch) if reinforcement bar is not greater than 12mm and 40mm (1.5-inch) if bar is greater than 12mm. Cover for a column is the distance between the surface of the concrete column and the nearest reinforcement.
Size of footing cover should be range between 40mm to 60mm (1.5-inch to 2.5-inch), or an average of 50mm (2-inch). Cover for a footing is the distance between the bottom surface of the concrete footing and the bottom surface of the reinforcement.
Size of slab cover should be at least 15mm (3/5- inch). Cover for a slab is the distance between the top surface of the concrete slab and the top surface of the reinforcement.
Clear cover for slab, beam, column, staircase and footing
The size of clear cover for slab, beam, column, staircase and footing should be depending on various factors like design of RCC structure, weather condition, wet and dry condition, heavy load structure, residential or commercial building,etc. The size of clear cover 40mm is apply for column, 25mm for beam,15 to 20 mm for slab, 15mm for staircase and 40 to 50mm for footing/Foundation.
Clear cover of Beam
Clear cover of Beam :– size of clear cover of beam should be ranging between 25 mm to 40 mm. Clear cover of size 25 mm is apply in presence of dry climatic environment and 35 mm to 40 mm size should be taken in presence of wet climatic environment or sea side location.
Clear cover for column
Clear cover for column :- The size of clear cover for column should be ranging between 40mm to 50mm (or 1.57 to 2 inches). Clear cover of size 40 mm is good for dry weather condition and 50 mm for wet moist weather condition.
Clear cover for Beam
Cover for beam:- the American code Institute (ACI – 318 -11 detail about cover for beam, it stated that minimum thickness of cover for beam should be 35 mm in case of rebar size less than 8 (25mm) number of bar in dry weather condition, and minimum cover of 40 mm should be used in case of wet moist weather condition and more than #8 number bar.
Clear cover for Beam :– size of clear cover for beam should be ranging between 25 mm to 40 mm. Clear cover of size 25 mm is apply in presence of dry climatic environment and 35 mm to 40 mm size should be taken in presence of wet climatic environment or sea side location.
Clear cover for column
Cover for column:- the American code Institute (ACI – 318 -11 detail about cover for column, it stated that minimum thickness of cover for column should be 40 mm in case of rebar size less than 8 (25mm) number of bar in dry weather condition, and minimum cover of 50 mm should be used in case of wet moist weather condition and more than #8 number bar.
Clear cover for column :-The size of the clear cover for column must be between 40mm and 50mm (1.5 to 2 inches). The clear 40mm cover is suitable for dry weather and the 50mm cover for wet and humid weather.
Clear cover of slab
Slab cover:- The size of the Clear cover for slab must be between 20mm and 30mm. The 20mm clear cover is designed for RCC Slab with a thickness of 4″ to 5″, 20mm for flat slab and 30mm for 6″ thick slab.
Clear cover for footing/ foundation
Clear cover of footing/ foundation :- The size of clear cover of footing/ foundation should be 40 mm to 75 mm. Clear cover size 40mm is used for general footing, clear cover of size 50mm is apply for Raft foundation top and 75mm for Raft foundation bottom/side.
Clear cover for retaining wall
Clear cover for retaining wall:– The size of clear cover for retaining wall should be ranging between 20mm to 30 mm.
Clear cover for strap beam
Clear cover for strap beam:- The size of clear cover for a strap beam should be ranging between 40mm to 50mm.
Clear cover for shear wall
Clear cover for shear wall:- The size of clear cover for shear wall should be a ranging between 20mm to 25mm.
Clear cover for staircase
Clear cover for staircase:- The size of clear cover for staircase should be ranging between 15mm to 20mm.
Clear cover for lintel
Clear cover for lintel :– The size of clear cover for lintel should be ranging between 15mm to 20mm.
Plinth beam cover
Size of cover for Plinth beam should be range between 25 mm to 40 mm. Clear cover of size 25 mm is apply in presence of dry climatic environment and 35 mm to 40 mm size should be taken in presence of wet climatic environment or sea side location.
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.
Conclusion:
The size of clear cover 40mm is apply for column, 25mm for beam,15 to 20 mm for slab, 15mm for staircase and 40 to 50mm for footing/Foundation.
Clear cover Sizes: 40mm is apply for column, 25mm for beam, 15-20mm for slab, 15mm for stair and 40-50mm for footing/foundation
