Civil Engineering Reference
In-Depth Information
using 1% of nanoparticles per cement mass was reported by He and Shi
(2008). Li
et al.
(2006) showed that nanoparticles are more favorable to
producing abrasion resistance in concrete than are polypropylene (PP)
fi bers. They also recorded that the abrasion resistance of concrete decreases
with its nanoparticle content and that the abrasion resistance of concrete
containing nano-TiO
2
is higher than that containing the same amount of
nano-SiO
2
. Chen and Lin (2009) used nano-silica particles to improve the
performance of sludge/clay mixtures for tile production. The results show
that nanoparticles improve the reduction of water absorption and lead to
an increase in abrasion and impact strength. A reduction in water absorp-
tion was reported by Givi
et al.
(2011). Ozyildirim and Zegetosky (2010)
used 4% nano-Fe
2
O
3
per cement mass and reported a reduction in the
permeability of the concrete. A reduction in permeability was also reported
for concrete in which 45% Portland cement was replaced by GGBFS con-
taining 4% nano-TiO
2
per cement mass (Khoshakhlagh
et al.
, 2012). Shekari
and Razzaghi (2011) compared the mechanical performance and the dura-
bility of concretes containing 1.5% of distinct nanoparticles (nano-ZrO
2
,
nano-TiO
2
, nano-Al
2
O
3
, nano-Fe
3
O
4
). They concluded that the nano-Al
2
O
3
is the most effective, but offered no explanation for the fi nding.
Nazari and Riahi (2011b) studied the performance of concrete in which
Portland cement was replaced by up to 2% nano-Al
2
O
3,
with an average
particle size of 15 nm. They reported that the optimum level of nano-Al
2
O
3
particle content was 1.0%. Jalal
et al.
(2012) showed that concretes contain-
ing 2% SiO
2
nanoparticles underperformed when compared to those pre-
pared with a mixture of 2% SiO
2
nanoparticles with the addition of 10%
micro-silica. This composition showed enhanced mechanical strength (Fig.
3.2) as well as improved durability. This was assessed by water absorption,
capillary water absorption, Cl ion percentage and electric resistivity (Fig.
3.3). According to Zhang and Li (2011), the pore structure of concrete
containing nano-TiO
2
is fi ner than that of concrete containing the same
amount of nano-SiO
2
. The resistance to chloride penetration of concretes
containing nano-TiO
2
is higher than that of concretes containing the same
amount of nano-SiO
2
.
This is explained by the particle diameter of nano-SiO
2
being smaller than
that of nano-TiO
2
, and the specifi c surface area of nano-SiO
2
being much
larger than that of nano-TiO
2.
The water requirement of concrete containing
nano-SiO
2
is therefore higher than that of concrete containing the same
amount of nano-TiO
2
. The authors also reported that the pore structure
refi nement increases with the content of nanoparticles (5%
<
3%
<
1%)
while chloride penetration decreases (5%
1%). These results par-
tially confi rm those previously obtained by Li
et al.
(2006). In their view,
the increased content of nanoparticles weakens the refi nement of the pore
structure of concrete. This may be attributed to the reduction of the distance
<
3%
<
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