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Fibre reinforced concrete
 

Fibre reinforced concrete

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Presentation at the fib Congress about variability of fibre reinforced concrete performances.

Presentation at the fib Congress about variability of fibre reinforced concrete performances.

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Fibre reinforced concrete Fibre reinforced concrete Presentation Transcript

  • Fibre Reinforced Concrete (FRC)
    • Laboratory Structures
    • Belgian Building Research Institute (BBRI)
    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 Katholieke Universiteit_Leuven
  • 1969 Steel fibres in concrete Can we replace common rebars ?
  • 2001 50 kg/m³ 6 cm Océanographic Museum (Valencia, Spain) Architect : F. Candela
  • FRC production in Belgium... 3%
  • Why not more ?
  • The wrong questions « What is de fibres dosage corresponding to x% rebars ? » 1
  • The wrong questions « What is the flexural resistance of concrete with x kg/m³ fibres ? » 2
  • The correct questions « What is the concrete compressive strength ? » « What is the application ? » « The workability issue » 2 3 1 / concepts « Do you know a design method ? » 4
  • Fibres with L=60mm and 30kg/m³ 138 000 fibres in 1 m³
  • X 3 12 samples 20 kg/m³ same fibre
  • The FRC problem is... due to... Variability ...3D orientation location of fibres
  • Is a FRC structure reliable ?
  • Variability influencing factors... Dosage 1 Fibre type 2 Testing method 3 Element geometry 4 Dosage Fibre type Testing method
  • FRC Mechanical properties in bending Deflection  Load Fibres dosage F r,0.46 >SLS< F r,3,00 >ULS<
  • Influence of the Testing method 1
  • FRC Mechanical properties in bending 4 tests methods EN 14651 4pt bending BEFIM Round plate
  • EN 14651 BEFIM HSC BEFIM EN 14651 HSC 4Pt Bending test 4Pt Bending test HSC Round Panel HSC Round Panel Test method Variability Residual stress @2,15/5mm 30kg/m³
  • Influence of the fibre type 2
  • Fibre type Variability Load [N/mm²] Deflection [mm] x 2
  • Fibre type Variability Load [N/mm²] Deflection [mm]
  • Influence of the Dosage 3
  • F r_ 0,46mm [N/mm²] X 2
  • Dupont (2003) Degrande & Deprez (2001) De Smedt & Wouters (2001) Brite Euram Project (2002) Relationship between thoughness (feq) and fibres dosage (Wf) ?
  • Coefficient of Variation [%] Dosage Variability ~50%
  • Coefficient of Variation [%] Dosage Variability ~50%
  • Vs.   Test parameter Design «  Do we use the good tool ?  »
  • Influence of the D/C level (Deflection/Cracking level) Load [N/mm²] Deflection [mm]
  • Performance depends on D/C level C > G > F > D > E > I > H f eq,2 C > F > G > D > E > I > H f eq,3 C > D > I > F > H > E > G F R,3.00 C > F > G > E > D > I > H F R,0.46 Classification based on absolute Value Residual / Energy
  • Performance highly depends on D/C level C > G > F > D > E > I > H f eq,2 C > F > G > D > E > I > H f eq,3 C > D > I > F > H > E > G F R,3.00 C > F > G > E > D > I > H F R,0.46 Classification based on absolute Value Residual / Energy
  • Performance depends on D/C level I > D > C > H > F > G > E W’ 40 mm G > C > D > I > F > E > H W’ 5 mm Classification based on absolute Value Energy
  • FRC classification So simple...?
  • Vs.   Reliability High thoughness P f x m x k
  • Variation ... increases with D/C level Variation ... depends on fibre type H(16)<I(21) < ... < F(31)<E(32) F R,3.00 I( 14 )<H(15) < ... < E(25)<F( 26 ) F R,0.46 Performance classification based on COV Residual stress
  • Correlations & Interpolations ...we need a plug’n play sytem !
  • Test method Correlation y = 1.87x - 3.3 R² = 0,99
  • r² Effect of dosage Interpolation
  •   The dosage dilemna
  •  
  • Workability Dosage fibres 38/50 100 kg/m³
  • Cracking tendency of FRC ?
  • Ring Bone tests
    • BBRI - Lab. Structures
    • [email_address]