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STEEL FIBRE REINFORCED CONCRETE (SFRC)

STEEL FIBRE REINFORCED CONCRETE (SFRC). for SLABS ON GRADE. Author: Royce Ratcliffe. FIBRES REINFORCE CONCRETE. Fibres – like all reinforcement - have their greatest effect after cracking develops. X-Ray Of SFRC. COMPARING FIBRES TO CONVENTIONAL REINFORCEMENT. MODEL. F c. F t = F c.

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STEEL FIBRE REINFORCED CONCRETE (SFRC)

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  1. STEEL FIBRE REINFORCED CONCRETE (SFRC) for SLABS ON GRADE Author: Royce Ratcliffe

  2. FIBRES REINFORCE CONCRETE Fibres – like all reinforcement - have their greatest effect after cracking develops.

  3. X-Ray Of SFRC

  4. COMPARING FIBRES TO CONVENTIONAL REINFORCEMENT

  5. MODEL Fc Ft = Fc d Ft REINFORCED CONCRETE STRESS BLOCK ACTUAL fc Ft Moment Capacity = Ft x d

  6. Fc ACTUAL EQUIVALENT fc 0.5D D Ft 0.9D ft f’t fe(from beam test) FIBRE CONCRETE STRESS BLOCK MODEL = fe bD2/6 Moment Capacity = f’tb.0.9D0.5D  f’t = 1/6/0.5/0.9 = 0.37fe

  7. DIRECT TENSION DIRECT TENSION FROM REINFORCEMENT BRIDGING CRACKS IN FLOOR SLABS WORKS TO KEEP THE CRACK NARROW, THEREBY MAINTAINING AGGREGATE INTERLOCK AND HENCE LOAD TRANSFER. NECESSARY AT SAW CUTS AND INTERNAL CRACKS TO MAINTAIN A HIGH LEVEL OF LOAD CARRYING CAPACITY IN THE SLAB. MESH – Ft = As . fy FIBRE – Ft = 0.37feBD

  8. TESTING THE REINFORCING PROPERTIES OF FIBRES

  9. Beam Testing

  10. International test methods:- 1. BEAM TESTS: Several variations on the same theme dependent on the country of origin. I.e. a beam of prismatic cross section is loaded at 1/3rd points with the deflection being at a controlled rate. P Height Width Span/3 Span/3 Span/3 ESTABLISHING REINFORCING PROPERTIES FOR SFRC

  11. Stress fe ESTABLISHING REINFORCING PROPERTIES FOR SFRC International test methods:- 1. BEAM TESTS: Several variations on the same theme dependent on the country of origin. I.e. a beam of prismatic cross section is loaded at 1/3rd points with the deflection being at a controlled rate. P Height Width Span/3 Span/3 Span/3

  12. First Crack Concrete Property .05-0.1 TYPICAL BEAM TEST RESULTS P or f P or f 1 2 3 Deflection (mm)

  13. Fibre/Matrix Property First Crack Strain Hardening Strain Softening .05-0.1 TYPICAL BEAM TEST RESULTS P or f 1 2 3 Deflection (mm)

  14. Square Panel

  15. Efnarc panel test The punching - flexion test is an ideal test European standard to check the SFRS behaviour: EN 14488 - 5 1) A shotcrete tunnel ling behaves like a slab 2) The hyperstatic test conditions allow load redistribution 3) The test can be carried out with mesh reinforcement This test was introduced in 1989 by the French Railway Authority, prior to being accepted and promoted by EFNARC then finally becoming a Euronorm (EN) in 2006.

  16. P Deflection EFNARC SQUARE (INDETERMINATE) PANEL TEST 100 x 100 P 500 x 500 600 x 600

  17. EFNARC SQUARE (INDETERMINATE) PANEL TEST 100 x 100 P 500 x 500 600 x 600 P High early toughness reinforcement Low toughness reinforcement Deflection

  18. 80 J 400 J 1250 J 800 J

  19. 0.5 vol % 4.55kg/m3 1.0 vol % 9.1kg/m3 1.0 vol % 9.1kg/m3 0.5 vol % 4.55kg/m3

  20. POLYPROPYLENE 1.0 vol % 9.1kg/m3 1250 J 0.5 vol % 40kg/m3 STEEL

  21. HOW FIBRES INCREASE LOAD CARRYING CAPACITY

  22. FULL SCALE TESTING 3000 3000 100 x 100 150 k = .035Nmm3

  23. P P Load fft P P P(fft) fft fe Deflection THEORETICAL SLAB RESPONSE

  24. P fe P P P fft fft THEORETICAL SLAB RESPONSE fe Load Deflection

  25. Ultimate Limit State Material Factor Load Factor Serviceability Limit State THEORETICAL SLAB RESPONSE Load Deflection

  26. Load Increasing Toughness(fe) Ultimate Ultimate Deflection PERFORMANCE VERSUS TOUGHNESS Ultimate Plain Concrete

  27. NEW PARADIGM LOAD CARRYING CAPACITY FOR FLOOR SLABS IS A FUNCTION OF FLEXURAL STRENGTH & TOUGHNESS

  28. ACTUAL RESULTS Beam Results P1(kN) PUlt(kN) 6 180 200 6 fe 6 fe Plain Concrete RC 60/60 30kg/m3 340 240 fe = 3.48N/mm2 RC 80/60 30kg/m3 >345 290 fe = 4.79N/mm2

  29. Polymeric Materials Creep occurs in the visco-elastic phase between Tglass & Tmelting Polypropylene Tglass = -100C Tmelting = 170-1800C CREEP Creep is the term used to describe the tendency of a material to move or to deform permanently to relieve stresses. Material deformation occurs as a result of long term exposure to levels of stress that are below the yield or ultimate strength of the material. Creep is more severe in materials that are subjected to heat for long periods and near melting point.

  30. CREEP

  31. THANK YOU!

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