Page 105 - New Trends in Eco efficient and Recycled Concrete

Recycled plastic 79

(2012) showed that mortar containing HIPS fine aggregates developed 87%, 69%
and 44% lower thermal conductivity compared to that of the conventional mortar at
the replacement level of 10%, 20% and 50%, respectively. Thermal conductivity of
concrete with 1% PET and 1% PP fibres was 18.0% and 21.8% lower than that of
the conventional concrete, respectively (Fraternali et al., 2011), suggesting that the
inclusion of PP leads to a concrete with higher thermal insulation than that of a con-
crete containing PET.

3.8 Final remarks

This chapter presented the properties of concrete containing recycled PA and PF.
Although the use of recycled plastic materials can be a promising technology to
reduce the environmental impact of both concrete and waste plastic, understanding
the behaviour of concretes containing recycled PA and PF is necessary to develop a
concrete with comparable properties to conventional concrete. Based on the discus-
sions presented in this chapter, the following conclusions can be drawn:
1. Replacement of NAs with smooth surface and spherical shape PAs results in an increase
in the workability of concrete. Concrete containing PAs with non-uniform shapes and PFs
exhibits a lower workability than conventional concrete.
2. An increase in the PA replacement level leads to a decrease in the compressive, flexural,
splitting tensile strength and elastic modulus of PA concrete. These properties of concrete
with low elastic modulus PA decrease more significantly than those with high elastic
modulus PA. Concrete containing PF with a fibre content up to a threshold amount (0.5%
of PP fibre and 1% of PET fibre) develops higher mechanical properties than those of
conventional concrete.
3. Although PA concrete exhibits a lower compressive strength, its ductility is higher than
that of the conventional concrete, which makes it suitable for use as a structural material
with a higher energy absorption capacity.
4. Owing to its higher porosity, recycled plastic concrete exhibits a higher water absorption
than that of the conventional concrete.
5. An increase in the amount of recycled PAs and PFs in concrete results in an increase in
the creep deformation of concrete. PA concrete develops a higher drying shrinkage,
whereas PF concrete develops a lower drying shrinkage than that of the conventional
concrete.
6. PA concrete exhibits a lower resistance to the elevated temperature than conventional

concrete at temperatures higher than 400 C owing to the creation of holes in the concrete.
On the other hand, the resistance of PF concrete to the elevated temperature is higher than
that of the conventional concrete because no spalling occurs in concrete containing PFs as
the vapour pressure is released when PF melts. Therefore, PF can be considered as a
promising material in the construction industry in applications in which high temperature
protection is required.
7. Owing to the lower thermal conductivity of recycled plastics than that of the NAs, con-
crete produced by recycled plastics develops a lower thermal conductivity compared to
that of the conventional concrete. Therefore, recycled plastic concrete can be used as a
thermal insulator in the construction industry to minimise thermal energy losses.