Few materials have had a greater effect on our way of life than concrete, a durable and versatile material widely used in construction. The problem is that concrete production entails huge environmental costs, including a huge carbon footprint.
The manufacture of cement, the main component of concrete, is responsible for an astonishing 7% of global carbon dioxide emissions, largely as a result of burning limestone to obtain calcium, which is essential for the reaction between cement and water to form the concrete.
However, according to experts at the University of Tokyo in Japan, it doesn’t have to be that way. University scientists created a new type of concrete with calcium carbonate, which can be derived from concrete waste at demolition sites, as well as CO2 captured from industrial exhaust gases.
The result, they say, is concrete that, if mass-produced, it can have a much smaller carbon footprint.
“Our concept is to acquire calcium from discarded concrete, which would otherwise go to waste,” explains Ippei Maruyama, a professor in the university’s Department of Architecture and a key member of the research team. “We combine this with carbon dioxide from industrial exhaust gases or even the air. And we do this at much lower temperatures than those used to extract calcium from limestone today. “
Concrete with calcium carbonate
Scientists say they were inspired for their invention by calcium carbonate deposits in marine ecosystems where dead organic matter solidifies into fossils. Then they began replacing calcium in concrete with calcium carbonate, a less carbon intensive substitute.
Calcium carbonate, they explain, is very stable, meaning it can function as a durable building material. However, the prototype version of concrete produced with calcium carbonate still cannot replace typical concrete because it is not as strong.
That said, it can be used in building smaller houses and other suitable structures.
“It is exciting to advance in this area, but there are still many challenges to be overcome”, warns Professor Takafumi Noguchi, who works at the same institution and was another member of the research team.
“In addition to increasing the strength and size limits of calcium carbonate concrete, it would be even better if we could further reduce the use of energy in the production process,” he explains.
“However, we expect that in the coming decades carbon neutral calcium carbonate concrete will become the common type of concrete and be one of the solutions to climate change,” adds Noguchi.
By Daniel T. Cross. Article in English