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

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. 1969

3. Océanographic Museum (Valencia, Spain)
Architect : F. Candela
2001
50 kg/m³
6 cm

4. FRC production
in Belgium... 3%

6. The wrong
questions
« What is de fibres
1 dosage corresponding to x%
rebars ? »

7. The wrong
questions
« What is the
2 flexural resistance
of concrete with x kg/m³
fibres ? »

8. 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 »

9. for L=60mm and 30kg
138 000
fibres in 1 m³

10. 12 samples
20 kg/m³
same fibre
X3

11. The FRC problem is...
Variability
due to...
...3D orientation
location
of fibres

12. Is this
reliable ?

13. Variability
influencing factors...
1 Dosage
2 Fibre type
3 Testing method
4 Element geometry

14. FRC Mechanical properties
Load in bending
Fibres dosage
FR,1
FR,4
0.5 3,5 Crack opening
Serviceability Ultimate

15. Influence of the
1 Testing method

16. FRC Mechanical properties
in bending
4 tests methods

17. 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

18. Influence of the
2 fibre type

19. 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]

20. 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]

21. C–D–E–F–G–H-I
In the following, these letters
indicate different fibre types

22. Influence of the
3 Dosage

23. fr,1 [N/mm²]
8
7
6
5
4 X2
3
2
1
0

24. 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)

25. Dosage
Coefficient of Variability
Variation [%]
60
50 FR,0.46
FR,3.00
40
30
20 ~50%
10
0

26. Dosage
Coefficient of Variability
Variation [%]
60
FR,0.46
50
FR,3.00
40
30
20 ~50%
10
0

27. « Do we use the
good tool ? »
Test parameter
Vs.
Design

28. 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]

29. D/C level is the
Deflection or Cracking Level
(which are correlated in function of the structural element)

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,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

31. 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

32. 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

33. FRC
classification
So simple...?

34. Vs.
Reliability
High thoughness
Pf
xk xm

35. 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

36. ...we need a
plug’n play sytem !
Correlations
&
Interpolations

37. 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

38. 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

39. The dosage
dilemna

41. fibres 38/50
100 kg/m³
Workability Dosage

42. Cracking tendency
&
tensile creep ?
use, for instance…

43. Ring
Bone tests

44. BBRI - Lab. Structures
bp@bbri.be
Time to
cross over ?