Concrete in Brief.pptx
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Properties of concreteWorkability
Segregation
Bleeding
Strength
Elasticity
Shrinkage
Creep
Durability
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Workability
Easily mixed, handled, transported, placed in
position and compacted
Segregation
Separation of constituent materials of concrete
Creates larger voids and reduces the durability
and strength
Bleeding
Water from concrete comes out of the surface
Produces pores in concrete and reduces strength.
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Strength
Compressive strength, tensile strength, flexural
strength
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Flexural testing
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Elasticity
Concrete not an elastic material
Stress in concrete astrains in initial stages
Influenced by elastic properties of aggregate,
mix proportion, age of concrete, type of
cement
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ShrinkageChange in volume of concrete due to loss of
moisture at different stages
Affects strength and durabilityLeads to the formation of cracks
Depends on constituents of concrete, size of
member, amount of water present in concreteand environmental conditions
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CreepGradual increase in strain without increase in
stress, with time
Depends on stress in concrete, age at loading andduration of loading
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Durability
Ability to resist weathering action, chemical
attack, abrasion or any other process of
deterioraton
Factors affecting are environment, cover to
embedded steel, type and quality of constituent
materials, cement content and water cement
ratio, workmanship to obtain full compaction,efficient curing and shape and size of member
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Types of concrete
Reinforced cement concreteFibre reinforced concrete
Ferrocement
Light weight concrete
Ready-mixed concrete
Shotcrete
Polymer concrete
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Fibre reinforced concrete
Fibres- natural materials like asbestos and
cellulose, or manufactured products such as
glass, steel carbon and polymer
Road pavements, industrial flooring, bridge
decks, canal linings, explosive resistant
structures etc.
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Ferrocement
Closely spaced, multiple layers of mesh or fine
rods completely surrounded by cement mortar.
Casting overhead water tanks, gober gas plants,
boat building, manhole covers, roofing units,
pressure pipes etc.
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Light weight concrete
Density lower than ordinary concrete
Light weight aggregates or introducing gas or airbubbles
long span bridges, fire protection for steel work
in tall buildings, filling for floor and roof slab
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Shotcrete
Shotcrete is a process where concrete is
projected or "shot" under pressure using a
feeder or "gun" onto a surface to form
structural shapes including walls, floors, androofs.
Shotcrete has high strength, durability, low
permeability, excellent bond and limitlessshape possibilities.
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Polymer concreteis part of group of concretes
that use polymers to supplement or replace
cement as a binder. The types include polymer-
impregnated concrete, polymer concrete, and
polymer-Portland-cement concrete.
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Ready-mixed concrete
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Advantages of cement concrete
Readily mouldedHigh compressive strength
Free from corrosion
Hardens with age
Resists abrasion
Impermeable
Provides good bond
Control properties of concrete
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Advantages of cement concrete
Mechanise completely its preparation
Adequate plasticity for mechanical working
More economical than steel
Compatible with other materials like steelDisadvantages
Low tensile strength
Self weight high
Not suitable for speedy construction-curing
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Admixtures and additives
Accelators
Admixtures which accelerate hardening/ development
of early strength.
Sodium carbonate,aluminiium chloride, potassium
carbonate, sodium aluminate etc
Set retarders
Admixtures which delay the setting of concrete
Common sugar, carbohydrate derivative
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Water reducers(plasticizers)
To achieve higher strength by decreasing water
cement ratio
To achieve same workability by decreasing
cement content
To increase the workability