How to mix old tires and building rubble to make sustainable roads
New material combines recycled concrete aggregate and rubber in a mix precisely optimised to meet road engineering safety standards

Date:
July 29, 2020
Source:
RMIT University
Summary:
A recycled blend brings together construction and tire waste, to
deliver both environmental and engineering benefits. The material
offers a zero- waste solution to a massive environmental challenge
- construction, renovation and demolition account for about 50%
of the waste produced annually worldwide, while around 1 billion
scrap tires are generated globally each year.



FULL STORY ========================================================================== Researchers have shown how a blend of old tires and building rubble could
be used as a sustainable road-making material, in a zero-waste solution
to boost recycling and support the circular economy.


========================================================================== Construction, renovation and demolition account for about half the
waste produced annually worldwide, while around 1 billion scrap tires
are generated globally each year.

The new material, developed by researchers at RMIT University in
Melbourne, Australia, is the first to combine recycled rubble and
rubber in a mix that is precisely optimised to meet road engineering
safety standards.

Designed to be used for base layers, the recycled blend is more flexible
than standard materials, making roads less prone to cracking.

Lead researcher Dr Mohammad Boroujeni said the rubble-rubber mix could
deliver both environmental and engineering benefits.

"Traditional road bases are made of unsustainable virgin materials --
quarried rock and natural sand," Boroujeni said.



==========================================================================
"Our blended material is a 100% recycled alternative that offers a new
way to reuse tire and building waste, while performing strongly on key
criteria like flexibility, strength and permanent deformation.

"As we push towards a circular economy that can eliminate waste and
support the continual use of resources, our recycled blend is the right
choice for better roads and a better environment." In Australia, only
16% of scrap tires are domestically recycled. About 3.15 million tons
of processed building rubble -- known as recycled concrete aggregate
(RCA) -- is added to stockpiles each year rather than being reused.

In 2019, federal and state governments agreed to ban the export of certain waste materials, with the aim of building Australia's capacity to generate
high value recycled commodities and associated demand. As part of the agreement, whole used tires will be banned from export by December 2021.

On the road to a circular economy Roads are made of four layers --
a subgrade, base and sub-base, with asphalt on top.



==========================================================================
All the layers must be strong enough to withstand the pressures of
heavy vehicles, while being flexible enough to allow the right amount
of movement so a road doesn't easily crack.

RCA can potentially be used on its own for road base layers, but adding recycled rubber can significantly enhance the finished product.

In previous research, the RMIT School of Engineering team has shown their rubble-rubber blend performs well when tested for stress, acid and water resistance, as well as strength, deformation and dynamic properties. Its
low shrinkage and good flexibility reduce the risk of cracking.

The new study published in Construction and Building Materials looked
at how the mix would withstand the pressures of being driven over by
countless vehicles over its lifetime.

Researchers used special machinery to assess the blended material's
performance under frictional force, or shear stress, and compared
different types of crumb rubber (fine and coarse) mixed into the RCA at different ratios.

The team identified an optimal mixture -- 0.5% fine crumb rubber to 99.5%
RCA - - that delivered on shear strength while maintaining good cohesion between the two materials.

Chief investigator Professor Jie Li said while the recycling of
construction waste and scrap tires was growing, both industries continued
to produce significantly more waste than is currently reused.

"Solutions to our waste problems will come not only from reducing how much
goes to landfill and increasing how much we recycle; developing new and innovative uses for our recycled materials is absolutely vital," Li said.


========================================================================== Story Source: Materials provided by RMIT_University. Original written
by Gosia Kaszubska.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Mohammad Saberian, Jie Li, Salpadoru Tholkamudalige
Anupiya. M. Perera,
Gang Ren, Rajeev Roychand, Hamayon Tokhi. An experimental study on
the shear behaviour of recycled concrete aggregate incorporating
recycled tyre waste. Construction and Building Materials, 2020;
264: 120266 DOI: 10.1016/j.conbuildmat.2020.120266 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200729114739.htm

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