The 1992 collapse of a gymnasium in the Atsugi air base as it was being constructed is one of hundreds of incidents in the history of using ready mixed concrete (RMC) in construction. Concrete is the second most used material after water on the planet and is responsible for 4.5% of global carbon emissions. The increased usage of RMC poses two main problems globally: the number of deaths in the construction industry and its contribution to carbon emissions. But students at MIT have found a solution that tackles both of these problems: concrete reinforced with radiated plastic.

The study, which was conducted by a group of undergraduate students and researchers, found that adding plastic flakes, pulverized by gamma rays into powder and adding it to concrete mix can create concrete that is stronger than the ready-mix concrete used around the world today.

Concrete block with radiated plastic.

Graphic of a concrete block made with radiated plastic (CC: MIT News)

The idea was born out of a Nuclear Systems Design Project at MIT, which aimed to find a novel way to lower carbon emissions. And to the students’ luck, concrete production happened to be one of the world’s greatest sources of it. But the challenges posed by this twofold problem were a kind of gridlock since many have tried to do the same in past experiments, only to produce a concrete that is weaker. Thus, the goal was to produce concrete that was both more robust and released less carbon emissions in the process.

The researchers used plastic bottles usually used for soda or water bottles. The group of students, including Carolyn Schaefer, a 2017 graduate of MIT, and Michael Ortega, a senior at MIT, found that when plastic bottles are bombarded with gamma rays, the crystalline structure of the plastic becomes more robust. The flakes from this process were then ground into powder, which is then mixed in with the other materials usually needed to make ready mixed concrete. They also found that the amount of gamma radiation that the plastic is exposed to is harmless, meaning it is safe to use in homes, offices, and other dwellings.

The experiments showed that cement mixed in with regular plastic that was not exposed to radiation was weaker than concrete that had no plastic at all, whereas the concrete mixed with radiated plastic proved to be 15% stronger than the former two concrete samples.

Researchers also found that emissions were reduced by about 0.0675% for the sample that they worked with – a reduction that came from swapping a mere 1.5% of concrete sans plastic with concrete mixed with radiated plastic. The team at MIT says that with further testing, the dent in the global carbon footprint will be larger.

Similar to the group at MIT, the U.S.-based ByFusion has also explored how to make concrete more environmentally-friendly. ByFusion produces concrete blocks that promise to produce 95% less carbon emissions than ordinary concrete production. The company hopes to also help decrease the amount of plastic released into our oceans annually by funnelling that plastic into something like the production of low-carbon emission concrete instead.

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