Page 102 - New Trends in Eco efficient and Recycled Concrete

76 New Trends in Eco-efficient and Recycled Concrete

200
0% EPS
Specific creep (με/MPa) 100 70%EPS
30% EPS
50% EPS
150

50

0
0 50 100 150
Curing age (days)
Figure 3.14 Comparison between specific creep of conventional concrete with EPS
aggregate concrete (Sabaa and Ravindrarajah, 1997). EPS, Expanded polystyrene.

seen in the figure, EPS concrete develops a higher specific creep than that of con-
ventional concrete (Sabaa and Ravindrarajah, 1997). It can also be seen in Fig. 3.14
that the initial creep rate of the concrete increased with an increase in RPA%.
Higher creep deformation of recycled plastic concrete than that of the conventional
concrete can be because PAs with low elastic modulus are unable to restrain the
creep deformation of the cement paste matrix (Sabaa and Ravindrarajah, 1997). It
was found that the addition of 0.3% and 1% PP fibre into the concrete resulted in
20% and 40% increase in the creep deformation of the concrete, respectively
(Houde et al., 1987).

3.6.2 Shrinkage

Shrinkage of concrete has a significant influence on the structural and durability-
related properties of concrete, which results in the acceleration of other damages
such as corrosion and freeze/thaw damage in the concrete (Kwon and Shah, 2008).
Shrinkage cracking is influenced by pore size, composition, curing method and
humidity conditions of concrete (Gribniak et al., 2013). Generally, concrete contain-
ing PAs develops a higher drying shrinkage than conventional concrete, which is
attributed to the lower elastic modulus of PAs than that of NAs (Ravindrarajah and
Tuck, 1994; Sabaa and Ravindrarajah, 1997; Chen and Liu, 2004; Tang et al.,
2008; Akcaozoglu et al., 2010; Fraj et al., 2010). The drying shrinkage of concrete
containing 55% EPS aggregates at 90 days was twice that of conventional concrete
(Chen and Liu, 2004). However, the drying shrinkage of concrete with some types
of PAs (e.g., PET and PVC) was lower compared to that of the conventional con-
crete (Kou et al., 2009; Silva et al., 2013). This can be because the amount of the
water absorbed by PAs is less than that of NAs, resulting in more available free
water for hydration in concrete.
The drying shrinkage of concrete containing PF has been reported to be lower
than that of conventional concrete (Sanjuan and Moragues, 1997; Song et al., 2005;
Wongtanakitcharoen and Naaman, 2007; Karahan and Atis, 2011; Choi et al.,
2011). This can be attributed to restraining the shrinkage because of the creation of