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Fibre reinforced concrete

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Fibre reinforced concrete

  1. 1. Fibre Reinforced Concrete Dispersion of the mechanical properties of FRC investigated by different bending tests ir. Benoit PARMENTIER ir. E. DE GROVE Prof. dr. ir. L. VANDEWALLE dr. ir. F. VAN RICKSTAL Laboratory Structures Katholieke Universiteit_Leuven Belgian Building Research Institute (BBRI)
  2. 2. 1969
  3. 3. Océanographic Museum (Valencia, Spain) Architect : F. Candela 2001 50 kg/m³ 6 cm
  4. 4. FRC production in Belgium... 3%
  5. 5. The wrong questions « What is de fibres 1 dosage corresponding to x% rebars ? »
  6. 6. The wrong questions « What is the 2 flexural resistance of concrete with x kg/m³ fibres ? »
  7. 7. The correct questions / concepts « What is the 1 concrete compressive strength ? » 2 « What is the application ? » 3 « What kind of fibre ? » 4 « Do you know a design method ? » 5 « The workability issue »
  8. 8. for L=60mm and 30kg 138 000 fibres in 1 m³
  9. 9. 12 samples 20 kg/m³ same fibre X3
  10. 10. The FRC problem is... Variability due to... ...3D orientation location of fibres
  11. 11. Is this reliable ?
  12. 12. Variability influencing factors... 1 Dosage 2 Fibre type 3 Testing method 4 Element geometry
  13. 13. FRC Mechanical properties Load in bending Fibres dosage FR,1 FR,4 0.5 3,5 Crack opening Serviceability Ultimate
  14. 14. Influence of the 1 Testing method
  15. 15. FRC Mechanical properties in bending 4 tests methods
  16. 16. Test method Variability Round Panel 4.3% BEFIM HSC 7.6% BEFIM 8.5% Round Panel HSC 8.8% 4Pt Bending test 15.9% 4Pt Bending test HSC 18.0% EN 14651 22.1% EN 14651 HSC 23.7% Residual stress @2,15/5mm 30kg/m³
  17. 17. Influence of the 2 fibre type
  18. 18. Load [kN] (6) Fibre types 35 Variability Type C 30 kg/m3 C30/37 Type D 30 kg/m3 30 30 kg/m³ Type E 30 kg/m3 Type F 30 kg/m3 25 Type G 30 kg/m3 20 Type H 4.5 kg/m3 Type I 4,5 kg/m3 15 10 5 x2 0 0 1 2 3 4 Mid-span Deflection [mm]
  19. 19. Load [kN] (6) Fibre types Type C 30 kg/m3 35 Variability Type D 30 kg/m3 C30/37 30 Type E 30 kg/m3 30 kg/m³ 25 Type F 30 kg/m3 Type G 30 kg/m3 20 Type I 4.5 kg/m3 15 10 5 0 0 10 20 30 40 50 Central Deflection [mm]
  20. 20. C–D–E–F–G–H-I In the following, these letters indicate different fibre types
  21. 21. Influence of the 3 Dosage
  22. 22. fr,1 [N/mm²] 8 7 6 5 4 X2 3 2 1 0
  23. 23. Some analytical relationships can predict the residual / equivalent stress in FRC Here is an example for Dramix RC 65/60 BN and equivalent stress according to the RILEM recommandations : ( )( f eq , 2 = 0,0217. f cm − 0,000119. f cm . 0,133.W f − 0,000574.W f2 2 ) Compressive resistance Fibres dosage [kg/m³] Dupont (2003) Degrande & Deprez (2001) De Smedt & Wouters (2001) Brite Euram Project (2002)
  24. 24. Dosage Coefficient of Variability Variation [%] 60 50 FR,0.46 FR,3.00 40 30 20 ~50% 10 0
  25. 25. Dosage Coefficient of Variability Variation [%] 60 FR,0.46 50 FR,3.00 40 30 20 ~50% 10 0
  26. 26. « Do we use the good tool ? » Test parameter Vs. Design
  27. 27. Load Influence of the [kN] 35 D/C level 30 Same post-crack strength 25 @ 5mm deflection 20 15 Different post-crack strength @ 40mm 10 5 0 0 10 20 30 40 50 Mid-span deflection [mm]
  28. 28. D/C level is the Deflection or Cracking Level (which are correlated in function of the structural element)
  29. 29. Residual / Energy Classification based on absolute Value feq,2 C>G>F>D>E>I>H feq,3 C>F>G>D>E>I>H FR,0.46 C>F>G>E>D>I>H Reminder : letters indicate different fibre types FR,3.00 C>D> I>F>H>E>G Performance depends on D/C level
  30. 30. Residual / Energy Classification based on absolute Value feq,2 C>G>F>D>E>I>H feq,3 C>F>G>D>E>I>H fR,1 C>F>G>E>D>I>H fR,4 C>D> I>F>H>E>G Performance highly depends on D/C level
  31. 31. Energy Classification based on absolute Value W’ up to 5 mm G>C>D>I >F>E>H W’ up to 40 mm I>D>C>H>F>G>E Performance depends on D/C level
  32. 32. FRC classification So simple...?
  33. 33. Vs. Reliability High thoughness Pf xk xm
  34. 34. Residual Performance classification based on COV stress fR,1 I(14)<H(15) < ... < E(25)<F(26) fR,4 H(16)<I(21) < ... < F(31)<E(32) Variation ...increases with D/C level Variation ...depends on fibre type
  35. 35. ...we need a plug’n play sytem ! Correlations & Interpolations
  36. 36. Test method 25 Correlation TYPE C - 30kg/m³ TYPE E - 30kg/m³ 20 y = 1.87x - 3.3 TYPE F - 30kg/m³ R² = 0,99 LINEAR GLOBAL 15 TYPE C - 30kg/m³ TYPE E - 30kg/m³ TYPE F - 30kg/m³ 10 LINEAR GLOBAL 5 0 0 5 10 15 20
  37. 37. Effect of dosage Interpolation R² of dosage influence 1.00 R² (F) R² (F+G) 0.95 0.90 r² 0.85 0.80 0.75 0.70 0.65 0.60 fR,0.46 fR,3.00 feq2 feq3
  38. 38. The dosage dilemna
  39. 39. fibres 38/50 100 kg/m³ Workability Dosage
  40. 40. Cracking tendency & tensile creep ? use, for instance…
  41. 41. Ring Bone tests
  42. 42. BBRI - Lab. Structures bp@bbri.be Time to cross over ?

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