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Waste rubber aggregates 95

strength reduction was 40% and 70%, respectively. The elastic modulus reduction
was 38% and 59% with the addition of 20% and 30% of rubber sand, respectively,
while the reduction in the tensile elastic modulus was 47.25% and 77.59%,
respectively.
A reduction in the compressive strength, splitting tensile strength and modulus
of elasticity of mortars was also found by Marques et al. (2008) by partially repla-
cing 12% natural sand with rubber (0 0.8 mm), by volume.
Jingfu and Yongqi (2008) investigated the flexural strength, after three, seven
and 28 days of curing, of mortars containing rubber (1.5 mm) as partial replacement
of natural sand at 0%, 8%, 16%, 21% and 31%, by volume, keeping the w/c ratio
constant. A reduction in the flexural strength with the addition of rubber sand was
reported. The reduction of the flexural strength after 28 days was about 15%, 26%,
41% and 59% with the addition of 8%, 16%, 21% and 31% of rubber sand,
respectively.
Oikonomou and Mavridou (2009) used worn automobile tyre rubber (size
0.75 1.18 mm) at up to 15%, by weight, keeping constant the w/c ratio. Results
showed a reduction in the compressive strength and flexural strength with the addi-
tion of rubber sand. The reduction in the compressive strength was about 24%,
47%, 60%, 72%, 76% and 78% with the addition of 2.5%, 5%, 7.5%, 10%, 12.5%
and 15% of rubber sand, respectively, while the reduction in the flexural strength
was 16%, 36%, 41%, 52%, 61% and 67%, respectively.
Turki et al. (2009a,b) reported on the partial replacement of natural sand
(0 2 mm) with rubber made from shredded worn tyres (1 4 mm) at 0%, 10%,
20%, 30%, 40% and 50%, by volume. The addition of rubber sand reduced com-
pressive and flexural strength. The reduction in the compressive strength was about
21%, 24%, 42%, 65% and 79% with the addition of 10%, 20%, 30%, 40% and
50% of rubber sand, respectively, while the reduction of the flexural strength was
about 38%, 38%, 53%, 65%, and 64%, respectively. The same authors reported a
reduction in the static and dynamic Young’s modulus of elasticity of mortars con-
taining rubber (size 1 4 mm) as partial replacement of natural sand (size 0 2 mm)
at 10%, 30% and 50%, by volume. The reduction in the static Young’s modulus
was about 60%, 80% and 90% with the addition of 10%, 20% and 50% rubber
sand, respectively, while the reduction in the dynamic Young’s modulus was about
13%, 56% and 67%, respectively.
Correia et al. (2010) reported a reduction in the compressive strength of mortars
by partially replacing natural sand (particle size below 2.4 mm) with waste vulca-
nised rubber scrap particles (,1.2 mm) at 10%, 20% and 30%, by weight. At w/c
ratio of 0.55, the reduction in the 28 days compressive strength was about 34%,
48% and 48% with the addition of 10%, 20% and 30%, respectively.
Experimental studies conducted by Corinaldesi et al. (2011) showed a reduction
in the 28 days compressive and flexural strength of mortars containing SBR or SR
as natural sand replacement. Natural sand (size 0 5 mm) was partially replaced
with either SBR (size 0 12 mm) or SR (size 0 8 mm) at 0%, 10% and 30%, by
volume. The reduction of the compressive strength after 28 days was about 30%
and 56% with the addition of 10% and 30% of SBR sand, respectively, while it was