Issue 60
T. Messas et alii, Frattura ed Integrità Strutturale, 60 (2022) 102-113; DOI: 10.3221/IGF-ESIS.60.08
In Fig. 12 the load-crack width curves obtained under three-point bending test for the specimens BFV7, BFV8, and BFV9 are reported, whereas in Fig. 12b those related to BFV3, BFV6 and BFV9 specimens are shown. The load- crack opening curves in Fig. 12 show a linear elastic trend up to a given load value corresponding to the nucleation of the first crack. The maximum load varies according to the fiber length and content. Then the trend is characterized by a load deceasing and an increasing in the crack opening. Finally, the curves become flattered (horizontal) and then vanishonly after a large crack, confirming that the specimens have reached their total failure (see Fig. 12a and Fig. 12b).
Fiber length 8 cm
Fiber content 1,8 %
10 12 14 16 18 20 22
10 12 14 16 18 20 22
BFV3 (0,6%) BFV6 (1,2%) BFV9 (1,8%)
BFV7 (L=2.5 cm) BFV8 (L=5 cm) BFV9 (L=8 cm)
0 2 4 6 8
0 2 4 6 8
Load (kN)
Load (kN)
0 1 2 3 4 5 Crack width (mm)
0 1 2 3 4 5 Crack width (mm)
(a) (b) Figure 12: Load-crack width curve: (a) for a fiber content of 1.8% and (b) for a fiber length of 8 cm.
20
3
20
3
Maximum crack opening (mm) Load (kN)
Maximum crack opening (mm) Load (kN)
15
15
2
2
10
10
(mm)
(mm)
1
1
Load (kN)
Load (kN)
5
5
1.20 %
0.60 %
Maximum crack opening
Maximum crack opening
0
0
0
0
0 1 2 3 4 5 6 7 8 9 10 Fiber length (cm)
0 1 2 3 4 5 6 7 8 9 10 Fiber length (cm)
(a)
(b)
3
20
15
2
10
(mm)
1
Load (kN)
5
Maximum crack opening (mm) Load (kN)
1.80 %
Maximum crack opening
0
0
0 1 2 3 4 5 6 7 8 9 10 Fiber length (cm)
(c) Figure 13: Maximum crack opening versus fiber length for fiber content: (a) 0.60 %, (b) 1.20 %, and (c) 1.80 % by volume. It can be observed that the fiber length is an important factor that greatly affects the mechanical behavior and cracking of the concrete for the different contents examined. Thus, the crack opening of the specimen reinforced with Alfa fibers of 8
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