Discarded plastic bottles could be used to make stronger concrete

MIT students have found a way to produce plastic-reinforced concrete that is up to 15% stronger than conventional concrete, by adding irradiated bits of plastic water bottles

MIT students have found a way to produce plastic-reinforced concrete that is up to 15% stronger than conventional concrete, by adding irradiated bits of plastic water bottles

Repurposing of plastic bottles is an optimal way of dealing with plastic waste, besides reduction of course, and way better than recycling. And what if they could be used to build more flexible concrete structures, from sidewalks and street barriers, to buildings and bridges? The research began as an undergraduate project in MIT, where scientists developed a method to fortify concrete, by adding plastic flakes –previously been exposed to small amounts of harmless gamma radiation and pulverized into a fine powder- and fly ash. The newly-discovered concrete mix is supposed to be up to 15 percent stronger than conventional concrete, while in the future, the team intends to experiment with different types of plastic, exposed to varying doses of gamma radiation, to determine their effects on concrete.

Concrete is, after water, the second most widely used material on Earth and approximately 4.5% of the world’s human-induced CO₂ are generated by manufacturing concrete. By replacing small portions of concrete with plastic that would otherwise end-up in the landfill, the cement industry’s global carbon footprint would be reduced, meaning that the discovery has far-reaching implications. “Our technology takes plastic out of the landfill, locks it up in concrete, and also uses less cement to make the concrete, which makes fewer carbon dioxide emissions,” says Michael Short, an assistant professor in MIT’s Department of Nuclear Science and Engineering. The team also includes Carolyn Schaefer ’17 and MIT senior Michael Ortega, who initiated the research as a class project; Kunal Kupwade-Patil, a research scientist in the Department of Civil and Environmental Engineering; Anne White, an associate professor in the Department of Nuclear Science and Engineering; Oral Büyüköztürk, a professor in the Department of Civil and Environmental Engineering; Carmen Soriano of Argonne National Laboratory. The new paper appears in the journal Waste Management.

The team exposed various batches of flakes to either a low or a high dose of gamma rays, a radiation type that is typically used commercially to decontaminate food.“At a nano-level, this irradiated plastic affects the crystallinity of concrete,” Kupwade-Patil says. “The irradiated plastic has some reactivity, and when it mixes with Portland cement and fly ash, all three together give the magic formula, and you get stronger concrete.” “We have observed that within the parameters of our test program, the higher the irradiated dose, the higher the strength of concrete, so further research is needed to tailor the mixture and optimize the process with irradiation for the most effective results,” he also adds, concluding that “the method has the potential to achieve sustainable solutions with improved performance for both structural and nonstructural applications.”

So far, the experiments have determined that substituting 1.5% of concrete with irradiated plastic significantly improves the mixture’s strength. While this seems a small percentage, it is enough to have a significant impact if implemented on a global scale. “Concrete produces about 4.5% of the world’s CO₂ emissions,” said Short. “Take out 1.5% of that, and you’re already talking about 0.0675% of the world’s carbon dioxide emissions. That’s a huge amount of greenhouse gases in one fell swoop.”