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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 1
M. K. EL DEBS | E.K. BELLUCIO
load versus displacement diagram (Figure 9) was performed.
Figure 10 shows the comparison between the average curves
of the PP12 and the reference mixture.
As expected, the strip of mortar made of the mixture with fi-
bers presented a better performance, as it resisted a greater
load in the evolution of the loading process. This strip had a
performance similar to the beginning of the loading of the ref-
erence mixture to the point of the first crack and the mixture
PP12 absorbed more load. The maximum load achieved by the
mixture PP12 was 53.65 kN to 4.53 mm of displacement. The
maximum load achieved by the reference mixture was 37.60
kN to 2.31 mm of displacement, which corresponds to 43%
increase in load and 96% increase in displacement.
The difference between the performances of the mortars is
clear, as presented in Figure 11. The reference mortar hardly
deformed due to the compression and the sample was com-
pletely in pieces. The sample with mortar PP12 deformed well
before cracking, and even with the cracks, the fibers allowed
the sample to remain complete.
b) Bending Test
In the strip bending test, six samples taken from each mixture
were used and an analysis of the load versus displacement
graphs was performed. The results are shown in Figure 12 and
Figure 13.
It was verified that each peak point in the curve corresponded
to a crack in the sample in samples with fibers. Thus, it can
be noted that the volumetric rate of the utilized fibers (2%) en-
sured the appearance of multiple cracks, which gives an ac-
ceptable degree of tenacity for the material. Comparing the
values of ultimate load of the graphics of the samples with and
without fibers, it is clear that the values are very close.
It can be seen in the photo in Figure 14 that the strip has a pro-
nounced curvature due to the good tenacity that fibers promote
to the material.
4.3 Bearing pads tests
a) Monotonic loading
The difference between the studied mixtures and the influ-
ence of surface roughness applied on the pads were ana-
lyzed through stiffness. The stiffness is the ratio of stress
versus
displacement of the pads, excluding the initial part of
the diagram which quantifies the ability of elastic deforma-
tion of the material.
To facilitate comprehension, the identification ‘LL’ was ad-
opted for pads with both sides smooth, ‘LR’ for pads with
one side smooth and one rough and ‘RR’ for pads with both
sides rough.
For this test 18 pads were casted in two stages: nine pads
were made in a first casting (being 3LL, and 3LR 3RR) and
other nine pads were made in a second casting. However,
through the results of the mixture PP12 it was possible to ob-
serve a significant difference between the two casts. Thus,
we chose to cast nine more pads of this mixture to confirm
these results. Even with a new casting the stiffness values
were quite different, especially for the LL and LR pads. Fig-
Table 2 – Results of stiffness average of monotonic tests (MPa/mm)
PP12 Mixture
1ª Casting
2ª Casting
3ª Casting
Average
LL
307
461
580
449
LR
286
386
444
372
RR
268
313
340
307
Reference Mixture
1ª Casting
2ª Casting
3ª Casting
Average
LL
636
649
-
642
LR
536
544
-
540
RR
473
506
-
490
Figure 17 – Stiffness comparison according
to the applied roughness