Page 52 from: Recycling Technology 2020

52
2020

Technolab

P
lastic waste can be crushed and used in
concrete, researchers at the University of
Bath and the University of Cambridge in

the UK have concluded. The academics are
convinced that plastic scrap is a ‘viable ingre-
dient’ for the construction industry.

Their research focussed on India, which is
currently facing a twin challenge of a national
sand shortage and the blight of plastic litter
(40% of India’s plastic waste is sent straight
to landfill). Collaborating researchers at Goa
University have confirmed the breakthrough
offers a two-fold solution.

Too much plastic, too little sand
Sand traditionally makes up about 30%

of concrete but, by incorporating 10% of fine
plastic residue, the researchers believe India
could save 820 million tonnes of sand a year.
This is great news for a nation experienc-
ing a rapidly growing urban population and
‘booming’ construction sector. In 2014 alone,
an estimated 280 000 tonnes of cement was
manufactured in India.

The sand shortage is said to be so acute

that it has sparked unregulated sand extrac-
tion from riverbeds, a practice that has re-
cently been banned in many Indian states.

Civil engineering specialist Dr John Orr,
who led the research project, says India cur-
rently produces 15 000 tonnes of plastic waste
daily and the lack of recycling facilities is a
major challenge.

A balancing act
‘Typically, when you put an inert, man-

made material like plastic into concrete, you
lose strength,’ Dr Orr points out. ‘This is be-
cause the plastic material doesn’t bond to the
cement paste in the material in the same way
that sand particle does.’

In order to improve that bonding, the
flakes were subjected to a 5% hypochlorite
solution and a 4% sodium hydroxide solu-
tion. The key element in the research was
to balance a small loss in strength with the
using worthwhile amounts of plastic. Dr Orr
reports that his team created and tested 11 dif-
ferent proportions of plastic to get the right
mix.

Only 12% less strength
The material used consisted of irregu-

larly shaped PET particles between 2.6 mm
and 11.4 mm, in quantities between 10% and
20%. The loss in tensile strength was only
about 12% and the researchers succeeded in
achieving a target compressive strength of 54
MPa to replicate that of traditional structural
concrete.

Dr Orr underlines: ‘We have proven that
end-of-life plastic really is a viable material for
use in some areas of construction that might
help us tackle the issues of not recycling the
plastic and meeting the demand for sand.’

This innovative research project was sup-
ported through funding from the British
Council under the United Kingdom India
Educational Research Initiative programme.

For more information, contact Dr Orr at:
[email protected]

Author:
Kirstin Linnenkoper

HigHLigHts

Research:
Plastic concrete

Pioneer:
University of Bath/Cambridge

Led by:
Dr John Orr

Plastic could be fantastic for
innovative eco-concrete
Wherever you look, plastic waste seems to be lying around on every street corner.
A group of UK researchers, however, argues that the construction industry could
easily use this material in ‘green’ concrete.

52_technolab-plastics.indd 52 12-09-19 14:24