Page 52 - Riem-Vol6_nº3

404 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
Study of the influential factors on the rheological behavior of adhesive mortar available in the market
applied by the mason for determining spreading and bead forma-
tion, it cannot be stated that Sample C does not provide satisfactory
spreading and bead formation. Probably the six studied mortars are
acceptable for use in coatings. The analysis that was performed was
comparative and the results obtained were restricted to the water/
dry material relationship indicated by the manufacturer.
Table 6 highlights the analyzed parameters of this research and
demonstrates the significant influence that particle size has on the
rheological behavior of the adhesive mortars studied compared
to the results obtained by the Squeeze Flow test. The numerous
influential parameters are indicated in this table as high (a), inter-
mediate (a) or low (a). Morphology is classified as either irregular
or regular. When the mortar exceeds a parameter, it is indicated
with a + sign.
Comparing the Squeeze Flow test results to the data obtained from
mortar property analysis, it was concluded that the primary influen-
tial parameter on the performance of the mortar used in this study
was particle size distribution of grains larger than 0.075 mm. Cal-
culating correlations between various properties analyzed, the per-
centage of aggregate retained between sieves with aperture 0.3 to
0.15 mm was shown to be more significant. This behavior might
best be explained by the phenomenon of imbrication of grains, i.e.,
rapprochement between the aggregates and the consequent fric-
tion between them during flow, which directly influence the yield
strength of mortar.
Samples A, C and D had a narrow distribution, which reduces the
average distance of separation between the particles and hinders
the flow. This effect was observed in the tests where mortar had
the highest compressive loads. It was determined in Sample C that
narrow particle size distribution was decisive in achieving supe-
rior maximum load compression. It was determined in Sample A
that narrow particle size distribution overcomes the effects of high
incorporated air levels, resulting in a compressive load inferior to
that of Sample C. Sample D exhibited low levels of incorporated air
and narrow particle size distribution resulting in a high compres-
sive load. Sample D also had a higher content of fines than the
other samples. It is possible that the water content of the mixture
was not sufficient to ensure adequate mixture flow.
Despite the similarities in particle size distribution between the
samples, the maximum compression loads were different. This is
probably due to the combined effect of high levels of incorporated
air in the mortar. The lowest compression loads were represented
by Samples E and F. Both of these samples had open size distribu-
tion but differed in the content of incorporated air.
In Sample E, grain size was decisive in compressive loading in
that it had more significant effect than a low level of incorporated
air. The low load compression level in Sample F resulted from high
levels of incorporated air, open particle size distribution and in the
morphological characteristics of particles highlighted by lower level
of roughness.
The observed results of the samples confirm the conclusions ob-
tained by Cardoso [14] in his doctoral thesis where he indicated
that open particle size resulted in smaller voids in the mortar and
lower loads in the Squeeze Flow test while narrow particle size dis-
tribution resulted in larger voids and higher loads in the Squeeze
Flow test.
The morphology of the aggregates allowed the verification of its in-
fluence on rheological behavior. Specifically in Sample F, rounded
grains acted together with incorporated air, particle size distribu-
tion and reduced compression load.
After analyzing the results, it was determined that it is likely that
there is a synergistic relationship between particle size distribution,
incorporated air content and morphology on the load compression
obtained in the Squeeze Flow test. However, it is noteworthy to
consider that, even with mortar additives, a portion of these ob-
served behaviors may have been due to these synergistic rela-
tionships, thus creating the necessity for further investigation on
the subject.
Figure 5 – Curve shape of load versus displacement of
adhesive mortars, obtained with the Squeeze Flow test
Table 6 – Summary of the adhesive mortars analysis
Adhesive
mortar
Compressive
load (N)
Paste viscosity
(mPa.s)
Particle size
distribution
Air entrained
content (%) Roundness
A
B
C
D
E
F
High (1.26)
Intermediate (1.20)
+ High (1.54)
High (1.21)
Low (0.62)
+ Low (0.48)
Intermediate (64)
Intermediate (66)
Intermed/Low (45)
Low (21)
Intermediate (66)
High (87)
Narrow
Open
+ Narrow
Narrow
+ Open
Open
+ High (28.2)
Intermediate (21.9)
High (22.9)
Low (15.7)
+ Low (15.5)
High (26.6)
Irregular (0.518)
Irregular (0.515)
Irregular (0.504)
Irregular (0.495)
Irregular (0.492)
Regular (0.616)