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Fibre reinforced concrete
- 1. PRESENTED BY :RAVIKIRAN KATTOLI
- 2. In allcountries, the construction industry is rapidly developing based on the invention of different materials and products in engineering fields. Engineers have attempted various types of materials in order to make the task more efficient reducing time, cost, improving durability, quality and performance of structures during their lifetime. Concrete is weak in tension and strong in compression. Even though reinforcement is provided in tension zone microcracks are developed in the tension and compression zone.
- 3. The propogationof these cracks can be arrested by using fibre reinforcement in concrete. The fibres are very small which are distributed over the whole area of concrete. Because of this we can not only arrest crack formation but also we can increase flexural, shear ,torsion, strength, freezing and thawing resistance.
- 4. It isa Small piece of reinforcing material possessing certain characteristic properties. It Can be circular or flat. Parameter used to describe fiber – “Aspect ratio”. Aspect ratio is ratio of its length to its diameter. Typical aspect ratio for fibers ranges from 30 to 150
- 5. Fiber reinforcedconcrete (FRC) is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers
- 6. Fibers havebeen used for concrete reinforcement since prehistoric times. In the early age, straw and mortar were used for producing mud bricks, and horsehair was used for their reinforcement. As the fiber technology developed, cement was reinforced by asbestos fibers in the early twentieth century. Later, the use of asbestos for concrete reinforcement was discouraged due to the detection of health risks. New materials like steel, glass, and synthetic fibers replaced asbestos for reinforcement. Active research is still in progress on this important technology.
- 7. 2.1 STEEL FIBERREINFORCED CONCRETE Steel fiber-reinforced concrete is basically cheaper and easier to use. Steel fiber-reinforced concrete uses thin steel wires mixed in with the cement.
- 8. This impartsthe concrete with greater structural strength and reduces cracking Steel fiber is often used in conjunction with rebar or one of the other fiber types.
- 9. Glass fiber-reinforcedconcrete uses fiberglass The glass fiber helps insulate the concrete in addition to making it stronger. Glass fiber also helps prevent the concrete from cracking over time due to mechanical or thermal stress. In addition, the glass fiber does not interfere with radio signals like the steel fiber reinforcement does.
- 10. Synthetic fiber-reinforcedconcrete uses plastic, nylon and polyproplene fibers to improve the concrete's strength. They help to improve the cement pumpability. The synthetic fibers do not expand in heat or contract in the cold which helps prevent cracking. Finally synthetic fibers help keep the concrete from spalling during impacts or fires. Polyproplene fiber
- 11. Historically, fiber-reinforcedconcrete have used natural fibers, such as hay or coir. While these fibers help the concrete's strength they can also make it weaker if too much is used. In addition if the natural fibers are rotting when they are mixed in then the rot can continue while in the concrete. This eventually leads to the concrete crumbling from the inside, which is why natural fibers are no longer used in construction. COIR HAY
- 12. 3.1. Volume offibres: low volume fraction (less then 1%): Used in slabs and pavement that have large exposed surface leading to shrinkage cracking Moderate volume fraction(between 1 and 2%): Used in construction method such as shotcrete High volume fraction (greater then 2%): Used in making high performance FRC
- 13. Aspect Ratiois the ratio of length of the Fibre to the diameter of its cross - section. Aspect Ratio = Length(L) / Diameter(D)
- 14. Aligned inthe direction of load Aligned in the direction perpendicular to load Randomly distribution of fibers
- 15. Fibre shouldbe significantly stiffer than matrix. Low modulus of fibres imparts more energy absorption while high modulus of fibres imparts strength and stiffness. Low modulus fibres e.g. nylon, polypropylene High modulus of elasticity e.g. steel, glass and carbon fibres.
- 16. Usage ofsteel fibres , higher aspect ratio and non-uniform distribution of fibres will reduce workability Prolonged external vibration fails to compact the concrete These properties can be improved by increasing water/cement ratio or by using water reducing admixtures
- 17. Restricted to10mm Friction between fibres and between fibres and aggregates controls orientation and distribution. 3.7. Mixing: Mixing of FRC needs careful precautions to avoid segregation Increase in aspect ratio, volume percentage and size of coarse aggregate will increase the difficulties.
- 18. Addition of4% of fibres report 2.5 times more increase in flexural strength. Presence of 3% of fibres develop 2.5 times more splitting tensile strength. Compressive strength- Improves(0-15 %). Toughness is about 20-40 times that of plain concrete. Impact strength is 5 to 10 times of plain concrete and improves wear and tear.
- 19. Main roleof fibres is to bridge the cracks that develop in concrete and increase the ductility of concrete elements. Improvement on Post-Cracking behaviour of concrete Imparts more resistance to Impact load Lowers the permeability of concrete matrix and thus reduce the bleeding of water
- 20. Increase inspecific gravity of the concrete. This means that the concrete will be heavier than normal concrete in case of some fibres Higher cost because of its control issues (production issues) as well as the cost of raw material is high. Corrosion of steel fibres
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- 25. More than400 tones of Shakti man Steel Fibers have been used recently in the construction of a road overlay for a project at Mathura (UP).
- 26. The efficientutilisation of fibrous concrete involves improved static and dynamic properties like tensile strength, energy absorbing characteristics, Impact strength and fatigue strength. The efficient utilisation of fibrous concrete involves improved static and dynamic properties like tensile strength, energy absorbing characteristics, Impact strength and fatigue strength. At elevated temperature, SFRC have more strength both in compression and tension.
- 27. Properties ofConcrete- Nevilla. Concrete Technology- MsShetty. ‘Fibre Reinforced Concrete’-N. Banthia ‘Synthetic Fibre Reinforcement for Concrete’- D. Ludirdja, J.F. Young, 1993. ‘Synthetic Fibres- Anne Laning, 1992. ‘Glass Fibre reinforced Concrete (GFRC)’ - By Wallace Neal, 1978. ‘Tensile behavior of Glass Fibre reinforced Concrete’- J.A.O.Barros, J.A.Figueiras, C.V.D.Veen