Old concrete could be constantly recycled into fresh bricks through a new process that also traps carbon dioxide.
Researchers led by the University of Tokyo used concrete from a demolished school building and carbon dioxide from the air to create new blocks strong enough to construct a house.
“The process involved grinding the old concrete into powder, reacting it with CO2 from the air, pressurising it in layers in a mould and finally heating it to form the new block,” the research report said.
“Instead of making buildings from new concrete only, this technique could offer a way to recycle old materials while also trapping carbon dioxide in the process. The blocks could theoretically be remade again and again, through the same process.”
Previously the University of Tokyo researchers had developed a new type of concrete that combined old concrete with carbon dioxide to create a durable material called calcium carbonate concrete.
The blocks created from this process were only a few centimetres long. The latest breakthrough overcame that limitation.
“We can make calcium carbonate concrete bricks large and strong enough to build regular houses and pavements,” researcher Professor Ippei Maruyama said.
“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.”
The research team will use the materials to construct a real two-story house by 2030. They also hope to establish a production facility to improve efficiency and give the concrete greater industrial application.
The full report can be found on the University of Tokyo website.
