Page 124 - New Trends in Eco efficient and Recycled Concrete

98 New Trends in Eco-efficient and Recycled Concrete

crumb rubber and tyre chips, at 5%, 15% and 25%, by total aggregate volume.
Reduction was greater as the rubber aggregate content increases.
Jingfu et al. (2009) replaced natural sand in concrete with the same volume of
3
rubber (0 1.5 mm) at 50, 80, 100 and 120 kg/m . Results showed a reduction in
the compressive strength, tensile elastic modulus and compressive elastic modulus
with the addition of rubber sand. The reduction of the compressive strength after 28
days of curing was about 4%, 1% and 14% with the addition of 50, 80, 100 and
3
120 kg/m of rubber sand, respectively. However, flexural strength after 28 days
was increased by adding rubber sand at 0.25%, 11.31% and 22.36%, respectively.
Raj et al. (2011) found a reduction in the compressive strength, splitting tensile
strength and modulus of elasticity by partially replacing natural sand at up to 20%
by volume, in SCCs with rubber (0 4.75 mm). The reduction of the mechanical
properties was more evident by increasing the rubber sand content.
The same authors found a reduction of the compressive strength of SCCs with
rubber sand addition (0 4.75 mm) as natural sand replacement at 5%, 10%, 15%
and 20%, by volume. The reduction of the compressive strength was about 8%,
16%, 23% and 40%, respectively.
Ozbay et al. (2011) found a reduction in the compressive strength of concrete
where natural sand was partially replaced with crumb rubber (0 3 mm) at 5%, 15%
and 25%, by volume. The reduction of the compressive strength was about 4%, 10%
and 26% with the addition of 5%, 15% and 25% of rubber sand, respectively.
Yung et al. (2013) replaced natural sand in SCC with waste tyre rubber at up to
20%, by volume. Two different particle sizes were used (0.3 and 0.6 mm), keeping
constant the w/c ratio. Results showed a reduction in the 1, 7, 28, 56 and 91 days
compressive strength with the addition of rubber sand. The reduction of the com-
pressive strength was about 9%, 22%, 16% and 29% with the addition of 5%, 10%,
15% and 20% of rubber sand (size of 0.6 mm), respectively, while it was approxi-
mately 3%, 26%, 27% and 31% with the addition of rubber sand (size of 0.3 mm).
Ganesan et al. (2013a,b) investigated the compressive and flexural strength of
rubberised SCCs. Natural sand was partially replaced with rubber (0 4.75 mm) at
15% and 20%, by volume. They also performed fatigue flexural tests, by applying a
maximum stress level ranging from 90% to 60% of the static flexural strength.
Tests were terminated when the number of cycles exceeded two million or when
the failure of specimens occurred. After 28 days of curing, compressive strength
was reduced by 6.85% and 13.35% with the addition of 15% and 20% of rubber
sand, respectively. On the contrary, static flexural strength increased when rubber
sand was added to the mix. Static flexural strength increased by 14% and 9% with
the addition of 15% and 20% of rubber sand, respectively. Fatigue flexural strength
increased as the rubber sand content increases. The enhancement of the fatigue flex-
ural strength was about 13% and 16% with the addition of 15% and 20% of rubber
sand, respectively.
Parveen et al. (2013) found a reduction in the mechanical properties of concrete
by partially replacing natural sand with crumb rubber (0.075 4.75 mm) at different
contents. Compressive strength was reduced by 11%, 23%, 31% and 37% with the
addition of 5%, 10%, 15% and 20% of rubber sand, respectively.