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Waste plastic could replace sand used in concrete

Bath uni plastic instead of sand in concrete 3to2

Waste plastic could be used to partially replace sand in concrete to make construction more sustainable, according to research by the University of Bath.

The research said it was possible to replace 10% of the sand in a concrete mix with waste plastic which had been ground down to similar sized granules as sand. Sand currently accounts for around 30% of a concrete’s mix.

The university said the resulting concrete was “almost as strong” as conventional concrete and estimated that by making the switch, around 820M.t of sand could be saved each year.

The research was carried out in conjunction with Goa Engineering College in India where the concrete was trialled. Bath University said the new concrete could help in places like India where there is a national shortage of sand and a vast quantity of plastic waste on the streets.

Five types of plastic in different sized particles were trialled, including those from recycled plastic bottles and recycled plastic bags. Plastic from recycled bottles, ground and graded to match the sand being replaced, was found to perform best in tests of concrete cubes and cylinders.

Cambridge University lecturer in concrete structures and principal investigator while working at University of Bath John Orr said: “Typically, when you put an inert, man-made material like plastic into concrete, you lose a bit of strength because the plastic material doesn’t bond to the cement paste in the material in the same way that a sand particle would.

“The key challenge here was to have a limit between a small reduction in strengths, which we achieved, and using an appropriate amount of plastic to make it worthwhile.

“It is really a viable material for use in some areas of construction that might help us to tackle issues of not being able to recycle the plastic and meeting a demand for sand.”

University of Bath co-investigator and reader in the department of architecture and civil engineering Richard Ball said: “Characteristics of the waste being added to the concrete, such as the type of plastic and the size and shape of the particles can all have an influence on the final concrete properties.

“Even when the reduction in performance prohibits structural applications lower tech uses such as paving slabs may be viable.”

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Readers' comments (1)

  • Still no mention of the life cycle of this product like the recycled plastic asphalt a few weeks back. Isn’t the problem we are all reading about daily being ground up microplastics ending up in the sea and watercourses, which in turn are being ingested by filter feeders and risking the whole food chain? So what happens to this plastic ‘sand’ in the concrete when demolished? Do we end up with unrecyclable concrete? Are we just creating another problem down the line?

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