Irradiated flakes of pulverised plastic strengthen concrete

If applied, the discovery by undergraduates at MIT could help cut carbon dioxide emissions associated with the production of cement and reduce the amount of plastic that goes to landfill.

“There is a huge amount of plastic that is landfilled every year,” said Michael Short, an assistant professor in MIT’s Department of Nuclear Science and Engineering. “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.”

Plastic has been introduced into cement mixtures before, but was found to weaken the resulting concrete. Exposing plastic to doses of gamma radiation, however, changes the material’s crystalline structure to make it stronger, stiffer, and tougher.

The students obtained flakes of polyethylene terephthalate — plastic material used to make bottles — from a local recycling facility and took them to MIT’s cobalt-60 irradiator, which emits the sort of gamma rays used commercially to decontaminate food.