Plastic waste is a viable partial replacement for sand in structural concrete, according to a new study by researchers from the UK and India. Their findings could help businesses in India dealing with a sand shortage while at the same time addressing the country’s immense plastic waste problem.
Concrete structures expert John Orr from the University of Bath led the study in partnership with researchers from Goa Engineering College, India. Their results, published in the journal Construction and Building Materials, show that replacing sand with similarly sized and shaped waste plastic particles from ground up plastic bottles produced concrete that was almost as strong as conventional concrete mixtures.
The researchers calculated that replacing 10% of sand in concrete with the plastic waste could save 820 million metric tons of sand a year. They tested the approach on concrete tubes and cylinders using five types of plastic particles in a variety of sizes. Ground up recycled plastic bottles that were graded to match the sand had the best performance.
“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,” Orr said. “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.”
Every day, 15,000 tons of plastic gets dumped in the country’s streets due to a lack of suitable recycling facilities, the researchers say.
At the same time, a booming construction sector and rapidly growing urban population in India are causing demand for sand in India to skyrocket, according to the researchers. The cost of sand is also rising, to the point where unregulated extraction from riverbeds is an enormous problem.
Globally, concrete accounts for about 9% of a new building’s budget even though it is responsible for nearly half the building’s carbon dioxide emissions, the researchers noted. “Each year, 4.2 trillion kilograms of cement is manufactured, resulting in about 1.9 cubic meters of concrete for every person on the planet,” they say.
Major companies that produce cement, which is an important ingredient in concrete, have struggled to decarbonize, a CDP report published earlier this year found.
“The companies that come out top in our research are addressing emissions by having new, highly efficient plants while also using a large amount of alternative materials that have lower emissions,” Marco Kisic, a senior analyst with CDP Investor Research, told Environmental Leader at the time.