Use of waste plastic in concrete could help support sustainable construction in India, say the researchers.
The Bath-led research has shown how replacing 10% of sand in concrete with waste plastic may help to reduce the vast amounts of plastic waste on India’s streets, and deal with a national sand shortage.
Research at the University of Bath has shown waste plastic to be a viable partial replacement for sand in structural concrete, providing one possible solution for future sustainable construction whilst addressing sand shortages in India.
The Bath-led research - in partnership with colleagues from Goa Engineering College, India – has been published in the journal Construction & Building Materials It demonstrates how the team investigated various different types of plastic to see if they could be crushed and used as a replacement for sand, which typically accounts for 30% of a concrete mixture.
Replacing sand with similarly sized and shaped waste plastic particles from ground-up plastic bottles was found to result in concrete that was almost as strong as conventional concrete mixtures. By replacing 10% of sand in concrete, it is calculated this approach could save 820 million tonnes of sand a year, and help reduce levels of plastic waste.
The researchers investigated the approach by testing concrete cubes and cylinders. Five types of plastic particles, including those from recycled plastic bottles and recycled plastic bags, were trialled in the mixes in a variety of sizes. Recycled plastic bottles, ground and graded to match the sand being replaced, were found to perform best.
Principal investigator and Cambridge University lecturer in concrete structures, Dr John Orr – who completed the research whilst working at the University of Bath – 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.”
Co-investigator and reader in the University of Bath’s Department of Architecture & Civil Engineering, Dr 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.”
The research was funded by the British Council under the UK India Education & Research Initiative (UKIERI) program, established in 2006 to foster greater educational links between the countries, including knowledge sharing and student mobility. The full research team consisted of Dr John Orr (University of Cambridge), Dr Richard Ball and James Thorneycroft (University of Bath), and Professor Purnanand Savoikar (Goa Engineering College, India).