Page 103 - New Trends in Eco efficient and Recycled Concrete

Recycled plastic 77

500
Conventional concrete
Drying shrinkage (με) 300 PVA concrete
Nylon concrete
400
PP concrete
200
100
0
0 20 40 60
Curing age (days)

Figure 3.15 Comparison between drying shrinkage of conventional concrete with nylon, PP
and PVA fibre concrete (Choi et al., 2011). PP, Polypropylene; PVA, polyvinyl alcohol.

shear strength along the interface of the fibre cement matrix when the matrix is
exposed to tensile stress resulting from shrinkage (Wongtanakitcharoen and
Naaman, 2007). Fig. 3.15 shows the comparison between the drying shrinkage
strain of conventional concrete with that of the nylon, PP and PVA fibre concrete
with a volume fraction of 0.2% (Choi et al., 2011). As can be seen in the figure,
nylon fibre concrete exhibited the lowest drying shrinkage, attributing to the higher
tensile strength of nylon fibre than that of the PP and PVA fibre. Furthermore, it
was reported that the unrestrained early age shrinkage of concrete containing
0.1% PP fibres was 32.5% lower than that of the conventional concrete
(Wongtanakitcharoen and Naaman, 2007). The drying shrinkage of the concrete
containing 0.05%, 0.1% and 0.2% PP fibres was 5%, 13% and 17% lower than that
of the conventional concrete at 210 days, respectively (Karahan and Atis, 2011).
On the other hand, inclusion of PP fibres did not have a remarkable influence on
the drying shrinkage of lightweight and recycled aggregate concrete (Kayali et al.,
1999; Kim et al., 2010). However, concrete containing 1% PET fibre developed
25% higher drying shrinkage compared to that of the conventional concrete at 50
days (Kim et al., 2010). This is because of the high volume of air voids in the con-
crete mix due to the presence of PFs.

3.7 Other properties

3.7.1 Resistance to elevated temperature
Limited information exists on the behaviour of recycled plastic concrete under
exposure to elevated temperatures. Albano et al. (2009) conducted a three-point
bending test on a beam in a furnace and reported that the flexural strength of con-

crete containing PET fine aggregate (with a melting point of 248 C) was identical

at 200 C, but lower at 400 and 600 C compared to those of the conventional con-
crete, which is because of the formation of holes in concrete from PET particles at

400 and 600 C. It was reported by Correia et al. (2014) that the concrete containing