Basic HTML Version
505
IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 4
B. F. TUTIKIAN | M. PACHECO
concrete while the mixture should be remade with different unit
composition components. After the 0.1% increase in admixture,
the flow test was performed again and it was verified that with
the added superplasticizer the result obtained was in accor-
dance with the established values. The remaining workability
tests were then performed, namely T50, “L-box”, “V-funnel”, so
as to verify the compliance of their results with the values given
by ABNT NBR 15823:2010 [4].
Once the unit composition test was defined, and through the re-
sults obtained, it was possible to calculate the final unit composi-
tions for the SCC. In order to calculate the amount of materials,
1 m³ worth of concrete was used, which was made up of 30% of
coarse aggregate and 70% of mortar. The mortar was composed
by 35% of fine aggregate while the remaining 65% was composed
by water, cement and admixture.
It should be noted that due to the procedures determined by the
method of dosage, it is necessary to maintain the same amount
of coarse and fine aggregates for all water/cement ratios outlined
in the initial step of the mixture procedure. This is relevant when
it is recommended that the amount of mortar should be adjusted
only for a water/cement ratio (the intermediate one, in the case of
the construction of the curve of the family of concrete with three
strengths). That implies that the only material which will be altered
for each concrete is the cement consumption, which will cause a
change in admixture consumption and amount of water. However,
from one mixture to another, water will be added and cement and
admixture will be reduced, considering for this group a constant
amount of 0.35 m³.
The final amount of superplasticizer admixture was 0.3% (only the
amount of solids), which is the equivalent of 0.75% if the amount
of solids and liquids existing in the admixture is considered. This
percentage is set for other unit compositions with the same aggre-
gate/cement ratio in mass, adjusting only the water/cement ratio.
Table 1 shows the unit composition for this method.
3.1.3 Tutikian-Dal Molin Method
The method is presented in schematic form in Fig. 4. The first step
taken in order to obtain the mixture was to determine the granu-
lar skeleton. The materials were packaged, two by two, starting
with the ones with the largest granulometry going all the way down
to the ones with the least granulometry. The first package of the
compression test was between the 25 mm gravel and the 19 mm
gravel, followed by the compacity with regular sand and, lastly,
with fine sand.
Table 2 shows the results of packaging the 25 mm gravel with the
19 mm gravel. It was observed that the mixture percentage which
provided the smallest number of voids was the one with 60% of 25
mm gravel and 40% 19 mm gravel, with 41.02% of voids. It should
be noted that the unit mass of this mixture is not the biggest of all,
i.e., the ideal ratio is always the one which results in a smaller num-
ber of voids. The compacted unit mass is only an indicator, since it
is not sufficient to reach a conclusion.
The second step of the packaging for the SCC mixture was obtain-
ing the compactness between the previous mixture, with 25 mm
gravel and 19 mm gravel, and regular sand. Table 3 shows the
result of the packaging of the gravel and the regular sand.
Lastly, the last packaging was performed, between the fine sand
and and previously packaged aggregates. Table 4 shows the re-
sults obtained from the compactness test of those materials.
It was observed that the optimal composition was 80% a mix of
25 mm and 19 mm gravel and regular sand with 20% fine sand,
which resulted in 16.61% worth of voids. The test was initiated with
substitutions from 10% to 10% and increased in precision to 5% as
it neared the ideal final value.
The compactness test values between materials resulted in the
following proportions for the SCC mixtures, in mass: 28.80% 25
mm gravel, 19.20% 19 mm gravel, 32% regular sand and 20%
fine sand.
Table 2 – packing test between 25 mm gravel and 19 mm gravel
25 mm Gravel
(%)
19 mm Gravel
(%)
Unit massa of
mixture (kg/m³)
Compacted bulk
density (kg/m³)
Index of voids
(%)
100
0
3065,00
1704,35
44,39
90
10
3044,50
1736,23
42,97
80
20
3024,00
1755,36
41,95
70
30
3003,50
1753,04
41,63
60
40
2983,00
1759,42
41,02
50
50
2962,50
1736,23
41,39
40
60
2942,00
1701,45
42,17
30
70
2921,50
1634,78
44,04
20
80
2901,00
1597,10
44,95
10
90
2880,50
1556,52
45,96
0
100
2860,00
1504,35
47,40