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A New Material Upgraded Modern Construction by Combining C02 With Recycled Concrete

Easing construction's reliance on calcium.

A new type of concrete has the potential to greatly reduce emissions from the construction industry, a press statement reveals. The calcium carbonate concrete, developed by researchers at the University of Tokyo, is made by combining waste concrete and C02 that can be sourced using carbon capture technologies. 

In 2018, think tank Chatham House said that cement, the main ingredient in concrete, was responsible for about 8 percent of global C02 emissions. This is largely due to the use of calcium in cement production, which is typically obtained by burning limestone. In a new paper published in the Journal of Advanced Concrete Technology, the University of Tokyo researchers detail their new method for taking waste concrete and captured carbon dioxide, and combining them using a newly-devised method.

The new process is, somewhat ironically, inspired by the way in which some aquatic lifeforms solidify into fossils over long periods of time. The researchers wondered whether the fossilization process, which forms hard calcium carbonate deposits where dead organic matter used to lie, could be harnessed to make concrete. 

"Our concept is to acquire calcium from discarded concrete, which is otherwise going to waste," said Professor Ippei Maruyama, one of the study's authors. "We combine this with carbon dioxide from industrial exhaust or even from the air. And we do this at much lower temperatures than those used to extract calcium from limestone at present."

A New Material Upgraded Modern Construction by Combining C02 With Recycled Concrete
Source: 2021 Maruyama et al.

Calcium carbonate concrete could go mainstream soon

The researchers' calcium carbonate concrete is very stable, meaning it has great potential as a construction material. It is also more sustainable than traditional concrete as it utilizes recycled concrete and C02 sourced from the air using carbon capture technologies. Unfortunately, it is not as strong as concrete, meaning that — in its current state — it's unlikely to be used for anything other than minor construction projects. Still, the University of Tokyo team aims to develop its material and they hope it can one day be mass-produced for large-scale use.

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"It is exciting to make progress in this area, but there are still many challenges to overcome," Professor Takafumi Noguchi, another one of the authors, said. "As well as increasing the strength and size limits of calcium carbonate concrete, it would be even better if we could further reduce the energy use of the production process. However, we hope that in the coming decades, carbon-neutral calcium carbonate concrete will become the mainstream type of concrete and will be one of the solutions to climate change."

Other construction methods also have a great deal of potential when it comes to reducing emissions. In August, researchers from the Technical University of Dresden announced that they are developing the world's first carbon concrete building and that the process they are using will cut carbon emissions by up to 50 percent. The same month, the United Kingdom announced that it was building part of its new high-speed rail network using a 3D printed concrete method that would also cut emissions in half. The University of Tokyo team's new method, therefore, has the potential to bolster existing efforts to reduce carbon emissions globally amid rising temperatures.

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