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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 3
Nanotechnology and Construction: use of nanoindentation measurements to predict macroscale elastic
properties of high strength cementitious composites
results, [21], and adjusted in order to obtain higher compressive
strength and spread diameter of ~180 mm in the flow-table test. The
mixing procedure is described in Table 4. After mixed and tested in
the fresh state, nine samples were molded for the tests in the hard-
ened state, whose details are described in the following sections.
2.3 Macroscale analysis
2.3.1 Macroscopic elastic modulus and strength
For the evaluation of elastic modulus and compressive strength six
prismatic specimens 40×40×160 mm
3
were molded. The molding
was performed in two layers of 2.0 cm, each one compacted under
a cycle of 15 seconds under vibration on a vibration table. The
samples were then sealed with plastic foil and kept in the mold for
24 hours. Later, the specimens were demolded and stored in water
for 20 days until the tests in the hardened state were performed.
Before testing, the top and bottom ends of the specimens were
polished to obtain flat parallel surfaces.
The uniaxial compression tests were performed by using an electro-
mechanical universal test machine (Testatron, Otto Wolpert-Werke
Gmbh). The load was measured by a beam load cell (MTS 100 kN)
attached to the electromechanical actuator. Two axial extensometers
with the gauge length of 50 mm were used to measure the displace-
ment of the specimen. The extensometers were located on the lateral
surfaces of the samples as indicated in Figure 1a. The centric loading
was checked at the beginning of the test and in case of any bending
occurrence, the test was stopped and the specimen adjusted to its
center position. The complete experimental set up is presented in Fig-
ure 1b,c. Four loading cycles were performed on each sample to ex-
clude the initial inelasticity (Figure 2a). The elastic modulus was com-
puted from the linear part of the last cycle in the stress-strain curve,
see Figure 1b. The loading continued until the ultimate load was
reached in order to obtain the compressive strength of each sample.
2.4 Microscale analysis
2.4.1 Nanoindentation tests
A cylindrical sample of 30 mm in diameter was prepared for na-
noindentation testing (Figure 3). The molding and curing proce-
filler, provided by Sklopísek Střeleč, CZ, with the maximum grain size
of 0.063 mm. A mix of two fine quartz sands, ST06/12 and ST01/06,
also provided by Sklopísek Střeleč, CZ, were used as aggregates
These are mainly composed by SiO
2
(99.2%) and Fe
2
O
3
(0.04%).
The sand mix included 50 vol.% of ST06/12 (with the grain size range
varying from 0.63 mm to 1.25 mm) and 50 vol.% of ST01/06 (with the
grain size range varying from 0.10 mm to 0.63 mm). The grain size
distribution of both the aggregates is presented in Table 2.
2.2 Mixture compositions and mixing procedure.
The compositions of mortar mixture in mass and volume is pre-
sented in Table 3. This composition was defined on previous study
Table 2 – Grain size distribution
of aggregates (in wt.%)
ST 01/06
ST 06/12
Middle grain size (d ) [mm]
50
0.38
0.88
AFS grain fineness number
30
14
3
Bulk density [kg/m ]
1500
1600
Grain size [
m
m]
ST 01/06
ST 06/12
>4000
-
-
>1250
-
7.0%
>1000
0.0%
-
>800
-
-
>630
12.0%
91%
>315
-
-
>200
85.0%
-
>100
2.0%
-
<100
1.0%
2.0%
Table 3 – Material density and mortar mixture composition, in mass and volume
Material
Density
[
3
kg/m ]
C1
Composition in
3
mass [kg/m ]
Composition in
3
3
volume [dm /m ]
Cement
3000
596.2
198.7
Quartz filler
2650
223.6
84.4
ST01/06
2650
633.4
239.0
ST06/12
2650
633.4
239.0
Admixture
1020
3.4
3.3
Water
1000
238.8
238.8