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8/9/2019 Fibre Reinforced Concrete.pptx
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FIBRE REINFORCED
CONCRETE
BUILDING TECHNOLOGY AND MANAGEMENT
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NEED
PCC has low tensile strength, limited ductility andlittle resistance to cracking
PCC develops micro-cracks, even before loading Addition of small, closely spaced and uniformly
distributed fibres act as crack arresters.
FIBRE REINFORCED CONCRETE is a
composite material consisting of mixtures of
cement, mortar or concrete and discontinuous,
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FACTORS AFFECTING THEPROPERTIES OF FRC
Relative Fibre Matrix Stiffness
Volume of Fibres
Aspect Ratio of the Fibre
Orientation of Fibres
Workability and Compaction of Concrete
Size of Coarse Aggregate
Mixing
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1. RELATIVE FIBRE MATRIXSTIFFNESS
Modulus of elasticity of matrix must be much
lower than that of fibre. E.g. steel, glass,
carbon
Fibres with low modulus of elasticity- nylon,
polypropylene
Interfacial bond between the matrix and the
fibres determine the effectiveness of stress
transfer
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2. VOLUME OF FIBRES
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3. ASPECT RATIO OF THE FIBRE
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Aspect Ratio of a fibre = Length/Diameter
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4. ORIENTATION OF FIBRES
The effect of randomness, was tested using
mortar specimens reinforced with 0.5% volume
of fibres, by orienting them:
parallel to the direction of the load
perpendicular to the direction of the load
in random
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5. Workability and Compaction of
Concrete
Fibres reduce workability
6. Size of Aggregate
Size of CA is restricted to 10mm
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7. MIXING
Cement content : 325 to 550 kg/m 3
W/C Ratio : 0.4 to 0.6
% of sand to total aggregate : 50 to 100%
Maximum Aggregate Size : 10 mm
Air-content : 6 to 9%
Fibre content : 0.5 to 2.5% by volof mix
: Steel -1% - 78kg/m 3 9
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TYPES OF FRCS
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STEEL FIBRE REINFORCEDCONCRETE (SFRC)
Aspect ratios of 30 to 250
Diameters vary from 0.25 mm to 0.75 mm
Hooks are provided at the ends to improve
bond with the matrix
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INTRODUCTION OF STEEL FIBRESMODIFIES:1. Tensile strength2. Compressive strength3. Flexural strength4. Shear strength5. Modulus of Elasticity6. Shrinkage7. Impact resistance8. Strain capacity/Toughness9. Durability10. Fatigue
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APPLICATIONS OF SFRC
Highway and airport pavements
Refractory linings
Canal linings
Industrial floorings and bridge-decks
Precast applications - wall and roof panels, pipes,
boats, staircase steps & manhole covers
Structural applications
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POLYPROPYLENE FIBREREINFORCED CONCRETE (PFRC)
Cheap, abundantly available
High chemical resistance
High melting point
Low modulus of elasticity
Applications in cladding panels and shotcrete 16
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GLASS FIBRE REINFORCEDCONCRETE (GFRC) High tensile strength, 1020 to 4080 N/mm 2
Lengths of 25mm are used
Improvement in impact strengths, to the tune of
1500% Increased flexural strength, ductility and
resistance to thermal shock
Used in formwork, swimming pools, ducts and
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OTHER FIBRES
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ASBESTOS FIBRES
High thermal, mechanical and chemicalresistance
Short in length (10 mm)
Flexural strength is 2 to 4 times that of
unreinforced matrix
Contains 8-16% of asbestos fibres by volume
Associated with health hazards, banned in
many countries
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CARBON FIBRES
Material of the future, expensive
High tensile strengths of 2110 to 2815 N/mm 2
Strength and stiffness superior to that of steel
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ORGANIC/VEGETABLE FIBRES
Jute, coir and bamboo are examples
They may undergo organic decay
Low modulus of elasticity, high impactstrength
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