In 2021, researchers introduced a groundbreaking recipe for eco-friendly concrete, incorporating building waste and CO2 into its formula. Fast forward to today, and the same innovative team has successfully utilized rubble from a demolished school and greenhouse gas to create bricks for new construction projects.
The Calcium Carbonate Circulation System for Construction (C4S) project, spearheaded by the University of Tokyo, revealed the significant environmental impact of traditional concrete production. A major factor contributing to this impact is the high temperatures required to heat limestone in order to produce calcium, a vital component of Portland cement.
Recognizing the limited reserves of limestone in countries like Japan, the research team focused on repurposing existing materials within the built environment. The original C4S project aimed to blend old concrete with carbon dioxide to generate a new building material known as calcium carbonate concrete. However, the resulting blocks were relatively small and possessed lower compressive strength.
The latest breakthrough involves transforming concrete from a demolished school into a fine powder, mixing it with CO2 from the air over a period of three months, and pressurizing the carbonated powder with a calcium bicarbonate solution. The resulting mixture is then molded and heated to produce robust building blocks suitable for constructing standard houses and pavements.
This innovative approach not only transforms old structures into valuable resources but also enables the recycling of calcium carbonate concrete bricks at the end of their lifespan. The team is committed to fostering a circular economy and achieving carbon neutrality through their research efforts.
The next phase of the C4S project will involve establishing a pilot plant to enhance efficiency and create larger building blocks for commercial production. By 2030, the team aims to construct a two-story house using calcium carbonate concrete bricks, showcasing the scalability and potential impact of their sustainable construction methods.
For more details on this groundbreaking development, refer to the published paper in the Journal of Advanced Concrete Technology by the University of Tokyo.
