Civil Engineering Reference
In-Depth Information
Fig. 4.35 Concrete specimens after the determination of tensile splitting strength, from left to
right: concrete with natural, pellet-shaped PET, fine and coarse PET flakes aggregates (Saikia and
de Brito
2010
)
28-day compressive strength and splitting tensile strength of concrete with PET
aggregates and an expression, f
st
= 1.40 9 (f
c
/10)
(1/3)
, for a similar relationship
for conventional concrete.
4.6.2.3 Modulus of Elasticity
According to ASTM C 469, the modulus of elasticity is defined as a stress-strain
ratio value for hardened concrete. The type of aggregates influences the modulus,
since the deformation produced in the concrete is partially related to the elastic
deformation of the aggregates.
From their study on the use of three different size fractions of PET waste
aggregates in concrete production, where concrete was prepared at two different
w/c values and at two different natural fine aggregates replacement levels, Albano
et al. (
2009
) observed higher modulus at lower substitution rate of NA by PET-
aggregates than at higher substitution rate and at low w/c value. They did not
observe any effect of particle size. The modulus of elasticity of concrete with PET-
aggregates met the requirement as described in ''American Manual of Reinforced
Concrete'' (1952) except the concrete composition with 20 % large PET-aggregate
at w/c of 0.60.
Frigione (
2010
) plotted the stress-strain curves (r-e curve) during the deter-
mination of the compressive strength of a reference concrete and a concrete with
PET with w/c = 0.45 and cement content of 400 kg/m
3
to determine the modulus
of elasticity. The calculated modulus was 48.1 and 41.8 GPa for the reference
concrete and the concrete with PET, respectively.
Hannawi et al. (
2010
) found that increasing the plastic content in concrete
decreased the resulting modulus of elasticity, probably due to the low stiffness of
PET and PC plastics as well as the poor bond between the matrix and plastic
aggregates (Fig.
4.36
a). Saikia and de Brito (
2010
) also found lower modulus of
elasticity for concrete with three differently shaped PET waste aggregates than for
