Fibre Reinforced Concrete.pptx

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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Documents

Fibre Reinforced Concrete.pptx