Concrete is one of the most widely used building materials in the world. However, its production contributes significantly to carbon emissions, making it one of the most carbon-intensive manufacturing methods. Researchers at VTT Technical Research Center in Finland are hoping to change this by creating carbon-negative concrete using a replacement for cement that can trap more CO2 than it takes to produce throughout its lifecycle.

The researchers experimented with different substitutes and discovered that slag from blast furnace smelting when combined with bio-ash could replace cement in concrete. Powdered slag can absorb more carbon than cement, and the VTT team figured out how to deposit CO2 from the air into powdered slag before putting it in cast concrete.

VTT senior scientist Tapio Vehmas said, “We have demonstrated in the pilot unit that our technology is capable of reducing the CO2 emissions of conventional concrete by 45%...by replacing Portland cement with slag.” Carbonaide, the VTT spin-out company, has secured nearly $2 million in funding to build a production center for its cast concrete blocks that will be capable of mineralizing “up to five tons of CO2 per day.”

The development of carbon-negative concrete could have significant implications for the construction industry and the fight against climate change. As one of the most commonly used building materials, reducing the carbon footprint of concrete could significantly reduce overall carbon emissions. The success of VTT’s experiment and the subsequent funding of Carbonaide's production center could pave the way for other companies to adopt similar methods and contribute to the growing trend of sustainable construction practices.