Page 127 - New Trends in Eco efficient and Recycled Concrete

Waste rubber aggregates 101

4.4.2.5 Replacement of natural aggregates with crumb rubber in
concrete (up to 50%)
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Topcu (1995) reported about the performance of concrete with rubber from used
tyres (size 0 1 and 1 4 mm), at up to 45%, by volume. No substantial changes
were observed after 7 and 28 days of curing up to 15% replacement ratio, while the
compressive strength decreased for a larger rubber ratio substitution.
Valadares et al. (2012) replaced natural sand in concrete with shredded rubber
(0 4 mm) at up to 35.77%, by volume. Compressive strength, splitting tensile
strength and modulus of elasticity were reduced by the addition of rubber sand.
This reduction increased by increasing rubber sand content. After 28 days of curing
compressive strength was reduced by 19%, 35% and 52% with the addition of
12.5%, 24.15% and 35.77% of rubber sand, respectively, while the splitting tensile
strength reduction was about 23%, 38% and 44%, respectively. The modulus of
elasticity decreased by 15%, 28% and 38% with the addition of 12.5%, 24.15% and
35.77% of rubber sand, respectively.
Mohammed et al. (2012) found a reduction in the compressive and splitting ten-
sile strength of hollow concrete blocks where natural sand was partially replaced
with rubber sand (0 0.6 mm) at 10%, 25% and 50%, by volume. This reduction
increased as the rubber content increases.
Ling (2012) reported a reduction in the compressive strength of concrete blocks
by replacing natural sand (0 4 mm) with rubber (1 5 mm) at up to 50%, by vol-
ume. W/b ratios varied between 0.45 and 0.55. Reduction increased by increasing
rubber sand content. After 28 days of curing, considering the concrete with w/c
equal to 0.45, compressive strength reduction was about 2%, 19%, 24%, 33%, 35%,
48%, 66% and 69% with the addition of 5%, 10%, 15%, 20%, 25%, 30%, 40% and
50% of rubber sand, respectively.

4.4.2.6 Replacement of natural aggregates with crumb rubber in
concrete (up to 100%)

Turgut and Yesilata (2008) found a reduction in the mechanical properties of con-
crete blocks where natural sand was replaced with crumb rubber (0.075 4.75 mm)
at different contents, by volume. The compressive strength reduction was about
12%, 33%, 57%, 69%, 81% and 84% with the addition of 10%, 20%, 30%, 40%,
50%, 60% and 70% of rubber sand, respectively, while the splitting strength reduc-
tion was 15%, 34%, 42 %, 53%, 70%, 85% and 86%, respectively.
El-Gammal et al. (2010) reported a reduction in the compressive strength and
elastic modulus of concrete by replacing natural sand and coarse aggregate with
crumb rubber (size 0.2 5 mm) at up to 100%, by weight. The compressive strength
reduction was about 80% and 81% with the addition of 50% and 100% of rubber
sand, respectively.
Issa and Salem (2013) realised concrete mixes by replacing natural sand and
crushed sand with crumb rubber (size 0.075 2.54 mm) at up to 100%, by volume.