Concrete is everywhere—in our roads, bridges, and towering skyscrapers. It’s a cornerstone of modern infrastructure, but it comes with a hefty environmental price. The cement used in concrete is responsible for about 8% of global CO2 emissions. If the cement industry were a country, it would rank as the fourth-largest emitter, just behind China, the US, and India.
But there’s hope on the horizon. Mehdi Khanzadeh, an assistant professor at Temple University, is working on a new kind of concrete called carbonatable concrete. This innovative material actually absorbs CO2 during its curing process, which could significantly cut down the construction sector’s carbon footprint. As Khanzadeh explains, “Carbonatable concrete is really only used in CMU blocks, which is a very limited portion of our industry. If we can address limitations through the method we are proposing, then we can open a much larger portion of our industry to implement carbonatable systems.”
The main challenge with carbonatable concrete has been its limited strength and durability, which confines its use to small, non-load-bearing applications like concrete masonry unit (CMU) blocks. Traditional methods restrict how much CO2 the material can absorb, which affects its sturdiness.
Khanzadeh’s latest research introduces a method called ‘internal-external CO2 curing.’ This approach boosts the carbonation depth, enhancing the material’s strength and durability. “We’re hoping that by using this process, we can move from only using carbonatable concrete for blocks and pavers to instead using the material for large-scale beams and columns,” Khanzadeh shares. Initial tests show promising results, with improvements in mechanical and durability performance by 80% to 100% over existing versions.
Since 2021, Khanzadeh has been refining this process, moving from small-scale tests to full concrete applications, ensuring thorough evaluations along the way. Now, he’s focused on scaling up production, considering factors like material availability, cost-effectiveness, and sustainability. “I try to keep in mind, even if this is successful, is it going to be applicable?” Khanzadeh ponders. “Is this material going to be scalable? This is especially important for something like concrete. We use it so much, so it needs to be accessible everywhere.”
While still in its proof-of-concept phase, Khanzadeh remains optimistic. Future tests will focus on the long-term durability of carbonatable concrete and its potential to be carbon-neutral or even carbon-negative. If successful, this development could revolutionize the construction industry, promoting sustainable practices while maintaining the strength and reliability we expect from traditional concrete.
