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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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**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. 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**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**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**2. Volume Of Fibres**FIBRE REINFORCED CONCRETE**3. Aspect Ratio of the Fibre**Aspect Ratio of a fibre = Length/Diameter FIBRE REINFORCED CONCRETE**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**5. Workability and Compaction of Concrete**Fibres reduce workability 6. Size of Aggregate Size of CA is restricted to 10mm FIBRE REINFORCED CONCRETE**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**Types Of Frc’s**FIBRE REINFORCED CONCRETE**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**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**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**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**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**Other Fibres**FIBRE REINFORCED CONCRETE**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**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**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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