Civil Engineering Reference
In-Depth Information
in a similar pattern representing an excellent way to reuse wastes like tyre
rubber.
Similar considerations can be made for PeT wastes. This polymeric
waste represents one of the most common plastics in solid urban waste
(Mello et al., 2009). in 2007 the world´s annual consumption represented
250 000 million terephthalate bottles (10 million tons of waste) with a growth
increase of 15%. In the United States 50 000 million bottles are landfilled
each year (gore, 2009). Since PeT waste is not biodegradable it can remain
in the environment for hundreds of years. Previous investigations already
confirmed the potential of PET waste in replacing aggregates in concrete
which represents a better option than landfill. In this work the most relevant
knowledge about the properties and the durability of concrete containing
polymeric wastes (tyre rubber and PeT wastes) will be reviewed.
13.2 Concrete with scrap-tyre wastes
13.2.1 Fresh concrete properties
Workability
cairns et al. (2004) used long and angular coarse rubber aggregates with a
maximum size of 20 mm, obtaining concretes with an acceptable workability for
low rubber content. These authors reported a reduction in the workability for
higher rubber content, since a rubber content of 50% led to a zero slump value.
other authors (guneyisi et al., 2004) studied concretes containing silica fume,
crumb rubber and tyre chips, reporting a decrease in slump with increasing
rubber content, with a 50% rubber content leading to mixtures without any
workability. The results obtained by those authors show that reducing the
water/concrete (W/c) ratio is associated with a decrease in the slump values
and that the silica fume worsens the workability performance.
Albano et al. (2005) replaced fine aggregates by 5% and 10% of scrap
rubber waste (particle sizes of 0.29 and 0.59 mm), reporting a decrease of
88% in concrete slump. Bignozzi and Sandrolini (2006) used scrap tyre
(0.5-2 mm) and crumb-tyre (0.05 to 0.7mm) to replace 22.2% and 33.3% of
fine aggregates in self-compacting concretes, commenting that the introduction
of the rubber particles does not influence the workability in a significant
way if the superplasticizer also increases. Skripkiunas et al. (2007) used
crumbed rubber to replace 23 kg of fine aggregates in concretes with 0.6%
of a polycarboxylic superplasticizer by cement mass obtaining the same
workability of the reference concrete. other authors (Batayneh et al., 2008)
used crumb rubber tyres (0.075-4.75 mm) in the concrete to replace sand
in various percentages (20%, 40%, 60% and 100%). These authors stated
that increasing rubber waste content decreases the concrete slump (Table
13.1).
