Page 56 - Riem-Vol6_nº3

401 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
M. R. M. M. COSTA | E. PEREIRA | R. G. PILEGGI | M. A. CINCOTTO
the No. 200 sieve (0.075 mm opening). Industrialized materials
were also utilized in a reconstruction approximating the amounts
of components in procedures recommended by Quarcioni [19].
The aggregate particles retained in sieve openings of 0.6, 0.3
and 0.15 mm were analyzed for their morphology in order to
determine texture differences and form irregularities between
the particles. The particles measuring above the 0.6 mm were
not analyzed due to the small amount within this range. The par-
ticle study was performed using images acquired by a stereo-
scopic Zeiss, Stemi model 2000-C. For each mortar, a minimum
of 100 grains were photographed in each sieve. Morphological
analysis of the aggregate was performed utilizing an IMAGO
program, version 2.2.4 loaned to us by the business ESSS[20].
The technique could not be applied to the portion of material
passing through the 0.075 mm sieve opening because of the
natural agglomeration of the grains. Their small size prevented
them from appearing individually in the images.
2.2.2 – Fresh state
In the fresh state mortar was rheologically evaluated by the
Squeeze Flow test, in addition to determining densities and the
amount of incorporated air. In characterizing the rheological be-
havior of adhesive mortar in the Squeeze Flow test, the flow of
material resulting from the application of a compressive load
on the fresh state sample caused shifts in its interior due to the
radial shear forces created during the flow. To execute this test
the equipment used was a universal test machine commonly
existing in building construction material laboratories for mea-
suring application load sample as described in NBR15839 [15].
The details of the test employed are indicated in Figure 1. The
movable punch has the same diameter as the sample in order to
ensure the load application on the entire surface.
In general, the rheological behavior expected for adhesive mor-
tar, throughout the test, was increased compression load as it
increases the displacement of the movable punch due to the ap-
proximation of the fraction larger than 0.075 mm in the mortar.
In practice, comparative analysis between the mortar enables
the identification of the ease of application by the mason and
how it forms over the toothed trowel.
The viscosity of the portion passing through the 0.075 mm sieve
opening (i.e., pulp) was measured in order to determine the in-
fluence of the fine fraction (paste) on the rheological behavior of
the mortar. This test was performed with a Brookfield Program-
mable Viscometer DV-II+ Version 5.0.
To determine the amount of air incorporated in the mixtures,
density tests were conducted in the fresh state, in addition to
bulk density test in the dry state as previously mentioned. Bulk
density in the fresh state was determined following the proce-
dure proposed by NBR 13278 [21].
3. Results and discussion
Table 2 reflects the proportion of coarse and fine fractions (paste)
adhesive mortar, or of material content larger than 75 micron and
size of less than 75 micron, respectively. The fine fraction is repre-
sented mostly by cement grains and fillers and the coarse fraction
by sand grains. Note that Sample D had a higher content of paste
than Sample E.
2.1 Definition of the sample universe
Initially, one bag each of thirty different brands of type AC-I ad-
hesive mortar [17] was acquired from building material dealers
throughout Brazil. Classification rules, based on manufacturer’s
specifications, were considered for the type AC-I mortar. In order to
reduce the initial sample size and provide a parameter for selecting
the mortars used in the research, each mortar was subjected to a
slip test, as determined by NBR 14085 [18]. In this test, the mortar
was applied on a substrate pattern and the strings were formed in
transverse direction to the substrate. Ceramic tiles were positioned
within the strings and the substrate was placed in an upright posi-
tion in order to observe for sliding of the tiles.
Based upon the sliding results, six brands were chosen for the
sample universe. Two brands were below the limit specified by
NBR 14081 [17]. Two were at the limit. And, two were above the
specified limit. The maximum sliding was specified at 0.7 mm.
Table 1 reflects the sliding results of the mortar chosen. The
relation of water/fine fraction dry material was obtained by mix-
ing with the water content specified by the mortar manufacturer
with respect to the proportion of fine fraction of each mortar.
For example, if the amount of water indicated for mortar A was
230 ml/kg and the fine fraction was 21.8% of the mortar mass,
then the ratio of water/dry material for mortar A would be equal
to 1.1, or 230 ml/218 g. The water content used was specified
by the manufacturer product packaging. Table 1 also reflects
the amount of water recommended by the mortar manufacturers
selected, in addition to the amount used.
2.2 Physical characteristics of the adhesive
mortars
2.2.1 – Anhydrous state
Mortar was physically characterized in the anhydrous state by
grain size and grain morphology. Bulk density was measured to
assist in determining the amount of incorporated air. We deter-
mined the complete granulometric curves by using screening
test, with the normal series of ABNT sieves, on the mortar and
a laser particle size analyzer for the fraction passing through
Figure 1 – Schematic representation of the
components of the Squeeze Flow Test