A COMPARATIVE STUDY OF COMPRESSIVE,

flexural, tensile AND shear STRENGTH OF

concrete with fibres of DIFFERENT ORIGINS..

BY:Abhijitsinh ParmarSD - 1010

Fibre reinforced concrete

• Concrete containing fibrous material which increases its structural integrity.

• It contains short discrete fibers that are uniformly distributed and randomly oriented.

• Fibres include steel fibres, glass fibres, synthetic fibres and natural fibres.

• Within these different fibres that character of fibre reinforced concrete changes with varying concretes, fibre materials, geometries, distribution, orientation and densities.

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Historical perspective• Fibres have been used as reinforcement since ancient

times. • Historically, horsehair was used in mortar and straw

in mud bricks. • In the early 1900s, asbestos fibres were used in

concrete, and in the 1950s the concept of composite materials came into being and fibre reinforced concrete was one of the topics of interest.

• By the 1960s, steel, glass (GFRC), and synthetic fibres such as polypropylene fibres were used in concrete, and research into new fibre reinforced concretes continues today.

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Effect of fibres in concrete

• Fibres are usually used in concrete to control cracking due to both plastic shrinkage and drying shrinkage.

• Also reduce the permeability of concrete and thus reduce bleeding of water.

• Some types of fibres produce greater impact, abrasion and shatter resistance in concrete.

• Do not increase the flexural strength of concrete, and so cannot replace moment resisting or structural steel reinforcement.

• Indeed, some fibres actually reduce the strength of concrete. However, fibres which are too long tend to "ball" in the mix and create workability problems.

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Steel Fibre

• Equivalent Diameter: 0.15 to 1.00 mm• Specific Gravity: 7840 kg/m3

• Tensile Strength:345 to 3000 MPa• Young’s Modulus: 200 GPa• Ultimate elongation: 4 to 10 %

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Glass Fibre

• Equivalent Diameter: 0.005 to 0.15 mm• Specific Gravity: 2500 kg/m3

• Tensile Strength: 1000 to 2600 MPa• Young’s Modulus: 70 to 80 GPa• Ultimate elongation: 1.5 to 3.5 %

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Carbon Fibre

• Equivalent Diameter: 0.3 to 0.35 mm• Specific Gravity: 1400 kg/m3

• Tensile Strength: 4000 MPa• Young’s Modulus: 230 to 240 GPa• Ultimate elongation: 1.4 to 1.8 %

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Coir Fibre

• Equivalent Diameter: 0.1 to 0.4 mm• Specific Gravity: 1120 to 1150 kg/m3

• Tensile Strength: 180 to 200 MPa• Young’s Modulus: 23 to 24 GPa• Ultimate elongation: 10 to 25 %

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Jute Fibre

• Equivalent Diameter: 0.1 to 0.2 mm• Specific Gravity: 1030 kg/m3

• Tensile Strength: 250 to 350 MPa• Young’s Modulus: 26 to 32 GPa• Ultimate elongation: 1.5 to 1.9 %

Shear strength

• L-shaped specimen.• Test was conducted on concrete

specimen at the age of 28 days.

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Shear test:

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Shear Test..

• Volume fraction 0.5%,1.0%,1.5%• Specimen shape:

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Compressive strength

• Compressive strength test on the cylindrical specimens in a 200t(2000 kn) capacity compressive machine.

• Loading rate : 140 kg/cm2/min

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Flexural Strength

• Beam specimen test on 1000 kn capacity universal testing machine.

• Four point flexure test at 7 kg/cm2/min

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Tensile Strength

• Cylindrical specimen.• Placed between two plate of testing

machine.• A plywood piece,3mm thick and 25 mm

wide inserted between plate and test specimen.

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Conclusion

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Compressive strength

• Steel fibre addition results in an increase of compressive strength of arround 20% relativeto plain concrete.

• Around 15% increase in recron and coir fibres.

• While for glass & jute fibres the increase in compressive strength is insignificant.

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Tensile strength

• Steel fibrous concrete – 30-35%• Recron & glass fibres – 25-30%• Coir & jute fibres – 15%

• The spilt tensile strength for fibrous concretes under the study was found to be in the range of 13.8 to 15.6% of compressive strength.

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Flexural strength

• The increase in flexural strength is as high as 48.38% in case of steel fibrous concrete and 25.23% in the case of jute fibrous concrete.

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Shear strength

• The contribution of fibres towards the shear strength of concrete was significant and an increase in shear strength of the order of 76.38% in case of steel fibrous concrete.

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Reference:

• Fiber Reinforced cement composites-Balaguru.

• The Indian Concrete Journal,Vol-82• ICI Journal Journal,Jan-2001• www.Wiki-pedia.com• www.Google.com

Thank You….

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