Civil Engineering Reference
In-Depth Information
following results: the limit of proportionality (fctl) and the residual
exural tensile
strength (fR,j) of the crack mouth opening displacements (CMOD) linked to the
crack openings of 0.5, 1.5, 2.5 and 3.5 mm (j = 1, 2, 3, 4 respectively). All the
mixes reached slump
fl
fl
ow test values of between 550 and 710 mm, which were
suf
cient to be able to pour the concrete into the beam formwork.
Table
4.2
shows the mechanical properties of the different concrete mixes for each
beam. Each of them had a Specimen ID for identi
cation (Table
4.2
) as follows:
{Concrete: with bers (HF) or without bers (H)}
{Top
fl
ange width, b
f
(mm)}
{
“
h
”
if the
-
-
depth of the beam is 800 mm, otherwise = 750 mm}
{
“
TR
”
with transverse reinforcement
-
equal to
ϕ
8@300 mm-2 legs}
{number of the beam}
-
For example, beam HF600TR/1 was made with
ber reinforced concrete
transversally reinforced with stirrups and had a top
ange width equal to 600 mm.
All the mechanical values (Table
4.2
) were obtained as the average of three
specimens 28 days after casting. In order to analyze production continuity, the mean
values, standard deviations (SD) and coef
fl
cients of variation (CoV) of the results
are included.
It is noteworthy that the FRC was observed to have brittle behavior during the
fl
exural tensile strength tests, as can be seen from the fact that fR,3 and fR,4 are
clearly lower than fR,2. A 2 mm crack opening was often reached with the sev-
erance of several
bers without them sliding out of the concrete, and sometimes a
brittle rupture occurred before being able to determine the residual strength of fR,3
and fR,4. A possible reason for this could be the combination of a high-strength
concrete matrix with steel
bers and low carbon (65/40BN). This should be taken
into account in future work. The values in Table
4.2
are those of at least two
specimens.
Table 4.2 Mechanical concrete properties (average values)
Specimen
ID
f
c
(MPa)
f
ctl
(MPa)
f
R1
(MPa)
f
R2
(MPa)
f
R3
(MPa)
f
R4
(MPa)
HF600TR/1
61.1
3.36
5.26
5.13
-
-
HF600TR/2
65.7
4.39
9.36
9.56
6.89
4.96
H600TR/3
52.4
3.64
-
-
-
-
HF600/4
65.4
4.70
10.46
7.99
6.24
5.12
HF600/5
65.9
4.20
8.55
8.43
5.55
3.92
HF400h/6
a
59.5
4.45
8.96
7.49
5.96
4.57
HF400/7
63.5
4.08
6.64
6.70
4.77
3.41
HF400/8
70.0
4.33
8.10
7.02
4.68
3.13
HF260/9
65.0
3.11
6.45
4.38
- -
Average 63.17 4.03 7.97 7.09 5.68 4.18
SD 4.75 0.51 1.61 1.59 0.79 0.75
CoV (%) 8 13 20 22 14 18
a
All the beams have a height of 750 mm with the exception of the HF400h/6 beam having a height
equal to 800 mm (this is indicated with the letter
''
h
''
whose signicance is explained in the text)
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