Concrete is, after water, the second most widely used material on the planet. The manufacturing of concrete generates about 4.5 percent of the world鈥檚 human-induced carbon dioxide emissions. Replacing even a small portion of concrete with irradiated plastic could thus help reduce the cement industry鈥檚 global carbon footprint. Reusing plastics as concrete additives could also redirect old water and soda bottles, the bulk of which would otherwise end up in a landfill.
鈥淭here is a huge amount of plastic that is landfilled every year,鈥� says Michael Short, an assistant professor in MIT鈥檚 Department of Nuclear Science and Engineering. 鈥淥ur 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. This has the potential to pull plastic landfill waste out of the landfill and into buildings, where it could actually help to make them stronger.鈥�
The team includes Carolyn Schaefer 鈥�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 B眉y眉k枚zt眉rk, a professor in the Department of Civil and Environmental Engineering; Carmen Soriano of Argonne National Laboratory; and Short. The new paper appears in the journal聽Waste Management.
鈥淭his is a part of our dedicated effort in our laboratory for involving undergraduates in outstanding research experiences dealing with innovations in search of new, better concrete materials with a diverse class of additives of different chemistries,鈥� says B眉y眉k枚zt眉rk, who is the director of Laboratory for Infrastructure Science and Sustainability. 鈥淭he findings from this undergraduate student project open a new arena in the search for solutions to sustainable infrastructure.鈥�
Schaefer and Ortega began to explore the possibility of plastic-reinforced concrete as part of 22.033 (Nuclear Systems Design Project), in which students were asked to pick their own project. 鈥淭hey wanted to find ways to lower carbon dioxide emissions that weren鈥檛 just, 鈥榣et鈥檚 build nuclear reactors,鈥欌�� Short says. 鈥淐oncrete production is one of the largest sources of carbon dioxide, and they got to thinking, 鈥榟ow could we attack that?鈥� They looked through the literature, and then an idea crystallized.鈥�
The students learned that others have tried to introduce plastic into cement mixtures, but the plastic weakened the resulting concrete. Investigating further, they found evidence that exposing plastic to doses of gamma radiation makes the material鈥檚 crystalline structure change in a way that the plastic becomes stronger, stiffer, and tougher. Would irradiating plastic actually work to strengthen concrete?
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