Page 118 - New Trends in Eco efficient and Recycled Concrete

92 New Trends in Eco-efficient and Recycled Concrete

4.3.2 Density

A reduction in the fresh density of concrete mixes containing waste rubber as par-
tial or total replacement of natural sand was observed by many authors. Albano
et al. (2005) reported a reduction of 20% up to 38% in the fresh density of concrete
mixes containing rubber from automobiles at 5% and 10%, by weight.
Balaha et al. (2007) reported a reduction in the fresh unit weight of concrete
mixes by partially replacing natural sand with ground waste tyre rubber (size
,4 mm) at 5%, 10%, 15% and 20%, by volume. This reduction increased as the
rubber sand content increases.
Topcu and Sarıdemir (2008) replaced natural fine aggregate with rubber (size
¸
0 1or1 4 mm) at 15%, 30% and 45%, by volume. The greater reduction in the
fresh unit weight values was observed in the concrete mix with coarse aggregates,
equal to 16.92%, while the reduction was smaller (1.13%) in the concrete mix with
fine aggregates.
Taha et al. (2008) observed a reduction in the fresh unit weight of concrete
mixes by replacing natural sand with rubber. The reduction was about 11%, 14%,
17% and 21%, by weight, with the addition of 25%, 50%, 75% and 100% of rubber
sand, respectively.
A reduction in the fresh density of mortar mixes with shredded rubber (size
0 2 mm) was also observed by Pedro et al., 2013. This reduction increased by
increasing rubber sand content. The reduction was 4.17%, 7.21% and 10%, by vol-
ume, with the addition of 5%, 10% and 15% rubber sand, respectively.
Bravo and de Brito (2012) observed a reduction in the fresh density of concrete
mixes by increasing the natural sand replacement with rubber made from used tyres
at 0%, 5%, 10% and 15%, by volume.
Thomas et al. (2014) reported a reduction in the fresh density of concrete mixes
by partially replacing natural sand with discarded tyre rubber particles. The reduc-
tion was 1% with the addition of 2.5% rubber sand up to 13.23% with the addition
of 20% rubber sand.
Experimental studies by Ozbay et al. (2011) showed a reduction in the fresh unit
weight of concrete mixes with the addition of crumb rubber (size 0 3 mm) as a
natural fine aggregate replacement. The reduction in the fresh unit weight was
0.91%, 3.32% and 5% with the addition of 5%, 15% and 25% rubber sand,
respectively.
Fadiel et al. (2014) partially replaced natural sand in mortar mixes with crumb
rubber with different sizes by keeping a constant w/c ratio. Results showed a reduc-
tion in the fresh unit weight of mortar mixes of 10%, 21%, 27% and 35% with the
addition of 10%, 20%, 30% and 40% rubber sand (size 0 0.6 mm), respectively,
while rubber sand with a size of 0.84 2 mm reduced the density by 6%, 16%, 22%
and 29%, respectively.
Mohammadi et al. (2014) reported a reduction in the fresh density of concrete
mixes by partially replacing natural sand with crumb rubber (after water-soaking
treatment) at 10%, 20%, 30% and 40%, by volume. This reduction increased as the
rubber sand content increases. At w/c ratio of 0.45, the reduction in the fresh