Page 90 - New Trends in Eco efficient and Recycled Concrete

64 New Trends in Eco-efficient and Recycled Concrete

0.1%
1 0.3%
0.5%
0%
2 0.05%
0.1%
0%
3 0.033%
0.065%
0.1% 0%
Reference 4 0.1%
0.05%

0% 0.2%
5 0.2%
0.3%
0.5%
0%
6 0.2%
0.3%
0.5%
0%
7 0.05%
0.18%
0.3%
0 100 200 300
Slump (mm)
Figure 3.2 Variation of slump of PF concrete with RPF%: 1 (Toutanji, 1999), 2 (Han et al.,
2005), 3 (Hsie et al., 2008), 4 (Karahan and Atis, 2011), 5, 6 (Nili and Afroughsabet, 2010):
PP fibre; 7 (Pelisser et al., 2012): PET fibre. % values represent RPF%. PF, Plastic fibre;
PP, Polypropylene; PET, polyethylene terephthalate.

Fig. 3.3A and B shows the variation of the density of concrete containing plas-
tic coarse and fine aggregates with RPA%, respectively. As can be seen in the fig-
ures, due to the lower specific gravity of PAs compared to that of NAs, the
density of PA concrete decreases significantly with an increase in RPA%. On the
other hand, because of the low volume fraction of PF added into the concrete, no
such significant decrease in the density of PF concrete is observed compared to
that of the conventional concrete (Kayali et al., 1999; Yao et al., 2003; Han et al.,
2005; Richardson, 2006; Karahan and Atis, 2011; de Oliveira and Castro-Gomes,
2011).
Previous studies have shown that the incorporation of PF in concrete has no
significant effect on its air content (Toutanji, 1999; Han et al., 2005; Richardson,
2006), whereas replacement of NAs with PAs increases the air content of the fresh
concrete. This can be attributed to the fact that, owing to the hydrophobic nature
of PAs, incorporation of PA in the concrete mix results in a poor concrete mixing,
whichleadstoanincreaseinits porosity (Ravindrarajah, 1999; Tang et al., 2008).
Ravindrarajah (1999) reported that replacement of natural coarse aggregates by
EPS aggregates up to 30% resulted in an increase in the entrapped air content up
to seven times of that of the conventional concrete.