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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 4
B. F. TUTIKIAN | M. PACHECO
4.2 Hardened state concrete properties comparisons
Firstly, the compressive strengths found at 7, 28 and 91 days will
be compared for the same individual unit compositions and after
the mixtures costs, as well as the modulus of elasticity, the propa-
gation velocity of the ultrasound wave, and the chloride ion pen-
etration, for the same compressive strength range.
In the Nan Su et al. method, it was not possible to execute the be-
havior equation and the dosage diagram, since only one unit com-
position was determined through it. Hence, so that the compari-
sons could be made, the base values resulting from this method of
dosage were used. For the other two experiments, Repette-Mello,
2005 [2], and Tutikian & Dal Molin, 2007 [3], the same individual
unit composition and compressive strength in the behavior equa-
tions will be sought, and they will be determined according to the
characteristic properties of those methods.
It should be noted that this comparison is valid, since the results
found by Nan Su et al., 2001 [1], are within the data limits estab-
lished in the hardened state properties achieved in the Repette-
Melo, 2005 [2], and Tutikian & Dal Molin, 2007 [3].
Table 9 shows the values established for the comparisons, in the
hardened state, between the three dosage experiments. The age
of 91 days will be the standard for the comparisons involving the
modulus of elasticity, propagation velocity of the ultrasound wave,
and chloride ion penetration.
4.2.1 Compressive strengths to 7, 28 and 91 days for the same
unit stroke
For this comparison, an individual unit composition (1:m) was
set. Through the behavior equations, the compressive strength
at 7, 28 and 91 days was searched, as shown in Fig. 7, and it
was possible to analyze which experiment reached the highest
compressive strength for the same individual unit composition
(1:4.28).
Observing Fig. 7, it can be concluded that the Tutikian & Dal Molin
method, 2007 [3], presented a compressive strength at 7 days 1%
higher than that presented by Nan Su et al., 2001 [1], and 29.5%
higher than that presented by Repette-Melo, 2005 [2]. It should
also be noted that, at 28 days, the Tutikian & Dal Molin method,
2007 [3], again achieved a higher compressive strength than the
other two methods. Its value was 6.8% higher than the one ob-
tained by Nan Su et al., 2001 [1], and 28.5% higher than that of
Repette-Melo, 2005 [2]. Lastly, it was verified that the Tutikian &
Dal Molin method, 2007 [3], was also superior regarding compres-
sive strength for the same individual unit composition, compared
to the two other methods. At 91 days the result found was 4.5%
higher than that of Nan Su et al., 2001 [1], and 29.1% higher than
that of Repette-Melo, 2005 [2].
4.2.2 Cost of mixtures for the same compressive strength
range at 7, 28 and 91 days
The cost comparisons, having the compressive strength set at 7
days, for all the methods, are shown in Fig. 8.
Based on the data presented in Fig. 8, it is observed that the Tu-
tikian & Dal Molin method, 2007 [3], presented, for the same com-
pressive strength range at 7 days, a cost which was 4.50% lower
than that obtained by Nan Su et al., 2001 [1], and 14.5% lower than
that obtained by Repette-Melo, 2005 [2].
For the same compressive strength range at 28 days, the Tutikian
& Dal Molin method, 2007 [3], presented an estimated result which
is 7.6% lower than that found by Nan Su et al., 2001 [1], and 14.9%
lower than the result found by Repette-Melo, 2005 [2].
Finally, it was observed that for the compressive strength at
91 days the Tutikian & Dal Molin method, 2007 [3], once again
obtained a value 6.1% lower than that by Nan Su et al., 2001
[1], and 14.4% lower than the value obtained by Repette-Melo,
2005 [2].
This behavior is probably owed to a better packaging of the ma-
terials promoted by the method of dosage and the lower admix-
ture consumption in relation to the amount of cement used in the
admixture. Better aggregate granulometric packaging enables
the mixture to boast fewer voids, thus obtaining a more homoge-
neous structure.
In the concretes dosed by the Tutikian & Dal Molin method, the
amount of superplasticizer admixture used was about 27% lower
than that used by Nan Su et al., 2001 [1], and approximately 17.3%
lower than that used by Repette-Melo, 2005 [2], thus favoring a
cost comparison.
Figure 7 – Compressive strength of
“j” days for the same unit trace 1:4,28
Figure 8 – cost comparison for the same
range of compressive strength of “j” days