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More sustainable concrete made from recycled concrete and CO2

Researchers at the University of Tokyo developed a more sustainable type of concrete made from waste concrete and carbon dioxide from the air or industrial exhaust gases.

Concrete is the most used material in the world of construction. It is durable and versatile, but comes with a dark side: around 7% of the world’s carbon dioxide emissions come from the manufacturing and use of cement, the main component of concrete. A large proportion of that 7% comes due to the use of calcium, which is commonly obtained by burning limestone.

The researchers at the University of Tokyo found a way to combine waste concrete and captured carbon dioxide and turn it into what is called calcium carbonate concrete.

The researchers, led by Professor Ippei Maruyama and Professor Takafumi Noguchi were inspired by the way some aquatic organisms Harden into fossils over time. This process forms hard calcium carbonate deposits on the organisms.

To make the concrete, they take calcium from discard concrete, which otherwise would go to waste. They then combine it with carbon dioxide from industrial exhaust or the air at much lower temperatures than those used to extract calcium from limestone.

Calcium carbonate is a stable material and makes for a durable construction material. However, calcium carbonate concrete cannot yet replace typical concrete as it is not as strong. For small houses and similar projects, this does not pose a problem, though. In addition, only small blocks of the concrete have been produced.

Image: University of Tokyo