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FIBRE REINFORCED CONCRETE

FIBRE REINFORCED CONCRETE. BUILDING TECHNOLOGY AND MANAGEMENT. NEED. 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.

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FIBRE REINFORCED CONCRETE

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  1. FIBRE REINFORCED CONCRETE BUILDING TECHNOLOGY AND MANAGEMENT

  2. NEED • 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. FIBRE REINFORCED CONCRETE

  3. 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 • Mixing FIBRE REINFORCED CONCRETE

  4. 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 FIBRE REINFORCED CONCRETE

  5. 2. Volume Of Fibres FIBRE REINFORCED CONCRETE

  6. 3. Aspect Ratio of the Fibre Aspect Ratio of a fibre = Length/Diameter FIBRE REINFORCED CONCRETE

  7. 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 FIBRE REINFORCED CONCRETE

  8. 5. Workability and Compaction of Concrete Fibres reduce workability 6. Size of Aggregate Size of CA is restricted to 10mm FIBRE REINFORCED CONCRETE

  9. 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 FIBRE REINFORCED CONCRETE

  10. Types Of Frc’s FIBRE REINFORCED CONCRETE

  11. 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 FIBRE REINFORCED CONCRETE

  12. FIBRE REINFORCED CONCRETE

  13. FIBRE REINFORCED CONCRETE

  14. Introduction of steel fibres modifies: • Tensile strength • Compressive strength • Flexural strength • Shear strength • Modulus of Elasticity • Shrinkage • Impact resistance • Strain capacity/Toughness • Durability • Fatigue FIBRE REINFORCED CONCRETE

  15. 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 FIBRE REINFORCED CONCRETE

  16. Polypropylene Fibre Reinforced Concrete (PFRC) • Cheap, abundantly available • High chemical resistance • High melting point • Low modulus of elasticity • Applications in cladding panels and shotcrete FIBRE REINFORCED CONCRETE

  17. 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. FIBRE REINFORCED CONCRETE

  18. Other Fibres FIBRE REINFORCED CONCRETE

  19. 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 FIBRE REINFORCED CONCRETE

  20. Carbon Fibres • Material of the future, expensive • High tensile strengths of 2110 to 2815 N/mm2 • Strength and stiffness superior to that of steel FIBRE REINFORCED CONCRETE

  21. Organic/Vegetable Fibres • Jute, coir and bamboo are examples • They may undergo organic decay • Low modulus of elasticity, high impact strength FIBRE REINFORCED CONCRETE

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