FIBRE REINFORCED CONCRETEBUILDING TECHNOLOGY AND MANAGEMENT

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PCC has low tensile strength, limited ductility

and little 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,

discrete, uniformly dispersed suitable fibres.

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FACTORS AFFECTING THE PROPERTIES 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

Mixing3

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1. RELATIVE FIBRE MATRIX STIFFNESS

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

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/m3

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 vol of

mix

: Steel -1% - 78kg/m3

: Glass -1% - 25 kg/m3

: Nylon -1% - 11 kg/m3

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TYPES OF FRC’S

Steel Fibre Reinforced Concrete (SFRC)

Polypropylene Fibre Reinforced Concrete (PFRC)

Glass Fibre Reinforced Concrete (GFRC)

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STEEL FIBRE REINFORCED CONCRETE (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 FIBRES MODIFIES:

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 FIBRE REINFORCED CONCRETE (PFRC)

Cheap, abundantly available

High chemical resistance

High melting point

Low modulus of elasticity

Applications in cladding panels and

shotcrete

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GLASS FIBRE REINFORCED CONCRETE (GFRC)

High tensile strength, 1020 to 4080 N/mm2

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 roofs, sewer lining etc.

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OTHER FIBRES

Asbestos Fibres

Carbon Fibres

Organic/Vegetable Fibres

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ASBESTOS FIBRES

High thermal, mechanical and chemical

resistance

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/mm2

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 impact

strength