Transforming Concrete into a Carbon Sink: MIT Engineers Unlock New Carbonation Pathways

In a groundbreaking development, MIT engineers have discovered innovative carbonation pathways that could transform concrete into an effective carbon sink, reducing its carbon footprint without compromising its mechanical properties. Concrete production currently accounts for around 8% of global carbon dioxide emissions.

Unlocking New Carbonation Pathways

The researchers, including MIT professors Admir Masic and Franz-Josef Ulm, MIT postdoc Damian Stefaniuk and doctoral student Marcin Hajduczek, and James Weaver from Harvard University’s Wyss Institute, published their findings in the journal PNAS Nexus. Concrete is the world's second most consumed material after water, forming the foundation of modern infrastructure.

While concrete has the potential to naturally absorb carbon dioxide from the atmosphere, these reactions can weaken the material and lower its internal alkalinity, leading to corrosion of the reinforcing rebar and negatively impacting its long-term mechanical performance.

Early Carbonate Formation: A Game Changer

The new carbon dioxide sequestration pathways rely on the early formation of carbonates during concrete mixing and pouring, before the material sets, largely eliminating the detrimental effects of carbon dioxide uptake after the material cures. The key to the new process is the addition of one simple, inexpensive ingredient: sodium bicarbonate, or baking soda.

In lab tests using sodium bicarbonate substitution, the team demonstrated that up to 15% of the total amount of carbon dioxide associated with cement production could be mineralized during these early stages. The resulting concrete sets much more quickly, without impacting its mechanical performance. This process allows the construction industry to be more productive, reducing the time required to complete a bridge or building.

Optimistic Future for Carbon-Neutral Construction Materials

These discoveries suggest an optimistic future for the development of carbon-neutral construction materials, and when combined with other recent innovations, could provide much greener, and even carbon-negative, construction materials for the built environment.