Research brings circularity to concrete blocks

The process involved grinding the old concrete into powder, reacting it with CO2 from the air, pressurising it in layers in a mould and heating it to form the new block.

This technique could offer a way to recycle old materials while also trapping carbon dioxide. The blocks could theoretically be remade repeatedly through the same process.

In 2021 researchers developed a new kind of concrete, which had the potential to reduce greenhouse gases and reuse waste from the construction industry.

The C4S project (Calcium Carbonate Circulation System for Construction) was led by Professor Takafumi Noguchi and included Professor Ippei Maruyama, who led on material development. They developed a method to combine old concrete with carbon dioxide, taken from the air or industrial exhaust, to create calcium carbonate concrete pieces that were only a few centimetres long.

They have now taken this technology to another level.

“We can make calcium carbonate concrete bricks large and strong enough to build regular houses and pavements,” Maruyama said in a statement. “These blocks can theoretically be used semi-permanently through repeated crushing and remaking, a process which requires relatively low energy consumption. Now, concrete in old buildings can be thought of as a kind of urban mine for creating new buildings.”