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IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 2
D. L. ARAÚJO | A. R. DANIN
|
M. B. MELO
|
P. F. RODRIGUES
the slump flow test by the Abrams cone method, conform to stan-
dard ABNT NBR 15823-2:2010 [25]. The results of these tests are
shown in Table 2.
In the center of each test specimen a steel bar was cast, whose di-
ameter varied between 10 mm, 12.5 mm, 16 mm, and 20 mm. The
average yield stress of these bars, previously determined following
standard ABNT NBR ISO 6892:2002 [26], was 592 MPa, 572 MPa,
616 MPa, and 505 MPa, respectively.
The tests with bars with diameter above 10 mm were called split-
ting tests, realized in order to evaluate the influence of the fibers
when the bonding failure happened through splitting of the con-
crete cover. The relationship between the concrete cover of the
reinforcement and its diameter (c/
φ
) varied during the tests be-
coarse aggregate that was used had maximum dimensions of 12.5
mm such as to guarantee that it would represent approximately
one-third of the length of the steel fibers, which had hooks at the
extremities, aspect ratio equal to 65 and length of 35 mm.
The prismatic test specimens were cast in horizontal position and
the concrete was consolidated with an immersion vibrator such
as to avoid the preferential alignment of the fibers in a specific
plane (Figure 2). The fresh concrete was characterized for work-
ability by a slump test, following standard ABNT NBR NM67:1998
[22], for air content in the mixture conform to standard ABNT NBR
NM47:2002 [23], and for density in accordance with standard
ABNT NBR 9833:2008 [24]. The concrete without fibers were self-
compacting, and for this reason its properties were determined by
Table 1 – Variables of pull-out and splitting tests
Test specimen
Fiber volume (%)
Bar diameter –
Φ
(mm)
Bonding length -
d
CP10.5.0.A1
CP10.5.0.A2
CP10.5.1.A1
CP10.5.1.A2
CP10.5.2.A1
CP10.5.2.A2
CP10.10.0.A1
CP10.10.0.A2
CP10.10.0.A3
CP10.10.0.A4
CP10.10.1.A1
CP10.10.1.A2
CP10.10.1.A3
CP10.10.1.A4
CP10.10.2.A1
CP10.10.2.A2
CP10.10.2.A3
CP10.10.2.A4
CP12,5.10.0.A1
CP12,5.10.0.A2
CP12,5.10.0.A3
CP16.10.0.A1
CP16.10.0.A2
CP16.10.0.A3
CP20.10.0.A1
CP20.10.0.A2
CP20.10.0.A3
CP20.10.1.A1
CP20.10.1.A2
CP20.10.1.A3
CP20.10.2.A1
CP20.10.2.A2
CP20.10.2.A3
10
10
10
10
10
10
12.5
16
20
20
20
0
1
2
0
1
2
0
0
0
1
2
5cm
5cm
5cm
10cm
10cm
10cm
12.5cm
16cm
20cm
20cm
20cm
5
5
5
10
10
10
10
10
10
10
10
1...,128,129,130,131,132,133,134,135,136,137 139,140,141,142,143,144,145,146,147,148,...190