Page 97 - New Trends in Eco efficient and Recycled Concrete

Recycled plastic 71

0%
0.1%
1 0.2%
0.3%
0%
0.1%
2 0.2%
0.3%
0%
0.1%
3 0.2%
0.3%
0%
0.5%
4 0.75%
1%
Reference 5 0% 0.1%
0.3%
0%
0.2%
6 0.3%
0.5%
0%
0.2%
7 0.5%
0.11%
0.47%
8 0.7%
0.93%
1.4%
0%
0.5%
9 0.18%
0.3%
0 2 4 6 8 10 12
Flexural strength (MPa)
Figure 3.9 Variation of flexural strength of PF concrete with RPF%. 1, 2, 3 (Suji et al., 2007),
4(Meddah and Bencheikh, 2009), 5 (Bagherzadeh et al., 2011), 6, 7 (Nili and Afroughsabet,
2010), 8 (Wang et al., 2000): PP fibre; 9 (Pelisser et al., 2012): PET fibre. % values represent
RPF%. PF, Plastic fibre; PET, polyethylene terephthalate; PP, polypropylene.
Fig. 3.9 shows the variation of 28-day flexural strength of PF concrete with RPF
%. It can be seen in the figure that, in most cases, the flexural strength of PF con-
crete is higher than that of the conventional concrete, which is because fibres carry
the applied load through the interfacial bond after the concrete cracks, thereby
providing resistance against the crack propagation and sudden failure of the con-
crete (Wang et al., 2013). As can also be seen in Fig. 3.9, an increase in RPF%
leads to an increase in the flexural strength of PF concrete. However, several stud-
ies reported that the flexural strength of PF concrete decreases with an increase in
RPF% above a certain threshold (Wang et al., 1994; 2000; Nibudey et al., 2013).
For example, Nibudey et al. (2013) showed that the flexural strength of PET fibre
concrete increased by 20.0% at 1% RPF% and decreased by 16.4% at 3% RPF%. It
was reported that fibre length had a remarkable effect on the flexural strength of PF
concrete (Meddah and Bencheikh, 2009). It was shown that the addition of 30-mm-
long PP fibres with RPF% of 1% in the concrete resulted in 44.4% increase in the
flexural strength of concrete, whereas the addition of 50- and 60-mm-long PP fibres
with the same RPF% led to no change in the flexural strength of concrete (Meddah
and Bencheikh, 2009).
Fig. 3.10 illustrates the variation of 28-day splitting tensile strength of PA
concrete with RPA%. As can be seen in the figure, similar to the compressive and