Page 51 - Riem-Vol6_nº3

403 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
M. R. M. M. COSTA | E. PEREIRA | R. G. PILEGGI | M. A. CINCOTTO
with the incorporated air content in fresh state mortar when using
the manufacturer designated water content.
In the results it was observed that the mortars had similar rounded
particles (in the range of 0.474 to 0.521 mm) except for Sample F
(fraction 0.3 mm sieve) which had superior rounding (0.792) com-
pared to the other samples. It is also possible to verify that mortar
clusters have similar elongation coefficients in the range of 0.662
to 0.755.
In regard to the bulk density of an anhydrous mixture, the mortar
exhibited variations in a very narrow range between 2.63 and 2.67
g/cm3. This can be attributed to the inherent variability of the test
method (on the order of 1.5%). However, for the mortar analyzed,
the differences resided in the fresh state bulk density which was in
the range between 1.46 and 1.71 g/cm3.
These differences may arise in chemical and physical changes
caused by the reactivity of cement, additives and the mixing
procedure, resulting in a distribution of constituents other than
that present in the anhydrous state. The cement determines hy-
drated components in the hardened mixture. Additives, and the
mixing procedure itself, will incorporate air into the fresh mixture.
Throughout the tests, there was a strong correlation between
fresh state bulk density and incorporated air content (R²=0.9693).
A variation in the level and type of additives can have a significant
impact on the behavior of fresh mortar. It was not the purpose of
this research to determine the quantitative data associated with
these variations.
Figure 4 reflects the viscosity of a mixture as a function of shear rate.
The data obtained in the tests indicated that all mixtures had
pseudoplastic behavior, i.e., there was a decrease in viscosity
with a corresponding increase in shear rate. Although, with dif-
ferent mortar viscosities between 0 a 50 S-1 , the data indicates
a tendency of similar viscosities at higher shear rates similar to
those in the Squeeze Flow tests. Thus, it was not considered
pertinent in this research to indicate viscosity as a variable in
the assessment of the rheological behavior of mortar. The profile
curves obtained in the Squeeze Flow test for adhesive mortar are
reflected in Figure 5.
The curves in Figure 5 show that adhesive mortar exhibits differ-
ent rheological characteristics as indicated by each mortar having
distinct compression loading absorption capacity when imposed by
the movable punch equipment.
Sample C had a higher compressive load as compared to the other
samples which resulted in greater spreading difficulty and deforma-
tion of the strings. Sample F had greater fluidity as compared to
the others which would result in easier spreading and formation of
the strings but would probably result in excessive slippage of the
ceramic tile. As it was not possible to obtain a parameter of effort
Table 4 – Morphological characterization of the coarse sand fraction in the adhesive mortars
Adhesive mortar Sieve
A mm mesh B C D E F
Roundness
Sphericity
0.15 mm
0.3 mm
0.6 mm
0.15 mm
0.3 mm
0.6 mm
100
50
30
100
50
30
0.518
0.521
0.500
0.728
0.738
0.729
0.509
0.525
0.504
0.706
0.734
0.699
0.508
0.502
0.474
0.730
0.700
0.662
0.492
0.522
0.516
0.678
0.729
0.720
0.492
0.490
0.521
0.717
0.685
0.733
0.506
0.792
0.496
0.735
0.755
0.696
Table 5 – Specific gravity and the air entrained content in the adhesive mortar
Adhesive mortar
A B C D E F
Specific gravity
Air entrained content
Dry
Fresh
Fresh
2.70
1.45
28.2
2.70
1.60
21.9
2.60
1.55
22.9
2.65
1.75
15.7
2.60
1.70
15.5
2.60
1.50
26.6
Figure 4 – Relation between viscosities
and shear rate of pastes