Re-Thinking Concrete

One of the big contributors to climate change is right beneath your feet, and transforming it could be a powerful solution for keeping greenhouse gases out of the atmosphere.

The production of cement, the binding element in concrete, accounts for roughly 7% of total global carbon dioxide emissions. That's about twice as much as the global airline industry.

Concrete is one of the most-used resources on Earth, with an estimated 26 billion tons produced annually worldwide. Given the scale of the industry and its greenhouse gas emissions, technologies that can reinvent concrete could have profound impacts on climate change.

So, engineers are busy designing the next generation of concrete technology that can reduce infrastructure’s carbon footprint and increase durability. That includes CO2-infused concrete that locks up the greenhouse gas and can be stronger and even bendable.

Concrete is made up of aggregate materials - primarily rocks and sand - along with cement and water. Because about 80% of concrete’s carbon footprint comes from cement, researchers have been working to find substitute materials.

Industrial byproducts such as iron slag and coal fly ash are now frequently used to reduce the amount of cement needed. The resulting concrete can have significantly lower emissions because of that change. Alternative binders, such as limestone calcined clay, can also reduce cement use. One study found that using limestone and calcinated clay could reduce emissions by at least 20% while also cutting production costs.

Apart from developing blended cements, researchers and companies are focusing on ways to use captured CO2 as an ingredient in the concrete itself, locking it away and preventing it from entering the atmosphere. CO2 can be added in the form of aggregates – or injected during mixing. Carbonation curing, also known as CO2 curing, can also be used after concrete has been cast.

These processes turn CO2 from a gas to a mineral, creating solid carbonates that also improve the strength of concrete. That means structures may need less cement, reducing the amount of related emissions.


Sustainable Construction Materials

The American Association for the Advancement of Science (AAAS) met last week to discuss lowering carbon emissions by erecting skyscrapers, amongst other buildings, out of wood. More...