Issue 31

A. Abrishambaf et alii, Frattura ed Integrità Strutturale, 31 (2015) 38-53; DOI: 10.3221/IGF-ESIS.31.04

compared (see Tab. 2). On the other hand, when the notch plane was parallel to concrete flow direction, a higher orientation factor observed comparing to specimens with θ =9 0 ° . Therefore, in θ = 0 ° series, a higher number of the effective fibres in the fracture surface was appeared which increased the concrete fracture parameters. Regarding the fibre segregation factor, the obtained average values of seg  were insignificantly higher than 0.5 meaning that a slight fibre segregation occurred through the panel’s depth. This could also justify the asymmetric crack opening width observed in the splitting tensile specimens.

θ= 0 °

θ= 90 °

f eff N [fibres/cm 2 ]

f eff N [fibres/cm 2 ]

 [-]

 [-]

f N [fibres/cm 2 ]

f N [fibres/cm 2 ]

η θ [-]

η θ [-]

Specimen Distance [cm]

seg

seg

B3 A4 C4 D3 B4 A5 A6 C6 D1

20.0 23.5 32.0 32.0 40.0 46.5 69.5 77.5 77.5

2.071 1.889 2.036 1.913 1.956 2.220 2.304 2.142 1.921 2.050

1.291 1.356 1.430 0.853 0.851 1.212 1.803 1.303 1.089

0.827 0.580 1.557 0.855 0.518 1.430 0.851 0.555 0.665 0.775 0.491 1.436 0.773 0.530 0.506 0.814 0.479 1.097 0.866 0.557 0.967 0.818 0.600 1.232 0.795 0.532 1.355 0.820 0.538 1.138

0.405 0.506 0.133 0.415 0.074 0.311 0.132 0.541 0.631

0.688 0.476 0.737 0.510 0.630 0.597 0.666 0.586 0.561 0.643 0.672 0.725 0.604 0.539 0.756 0.485 0.760 0.594 0.675 0.573 10.20 14.00

Average CoV (%)

1.24

0.35

7.16

23.74

4.15 7.33

31.98

57.11

Table 2 : Fibre distribution parameters.

110

60

102

Figure 8 : Localization of the plane surface considered in the fibre distribution assessment (units in mm).

Fig. 9 illustrates the orientation profiles obtained for each average orientation factor in comparison to both the two dimensional ( 2D ) distribution,   = 2 /π , [18] and the three-dimensional (3 D ) isotropic uniform random fibre distribution,   = 0.5, [19]. It was shown that the fibre orientation profile followed a Gaussian distribution [20, 21]. The orientation profile for θ= 0 ° series was represented by a distribution shifted to the left side, while for θ= 90 ° series the distribution profile tends to the right side. Therefore, within the specimens of θ= 0 ° series, fibres have a tendency to be aligned more perpendicular to the studied plane. The obtained distribution profile for the θ= 0 ° series was completely distinct from either the 2 D or 3 D theoretical isotropic uniform random distributions. Meanwhile, the distribution obtained for the θ= 90 ° series was very similar to the 2 D theoretical distribution. In conclusion, for SFRSCC laminar structures, assuming a 2 D or 3 D uniform fibre random distribution may be far from the reality, since the influence of fibre orientation due to the concrete flow also needs to be taken in to the account. Fig. 10 shows the exponential relationship between the number of fibres, f N , and effective fibres, f eff N .

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