Concrete is often overlooked despite being nearly everywhere in our daily lives, from buildings to roadways and other infrastructure. Thirty billion tons of concrete is produced each year, and a major concrete component — cement — produces 8% of the world’s carbon footprint. 

Traditional concrete naturally absorbs carbon dioxide, but the process takes decades or centuries, and it doesn’t absorb a large amount. A Purdue University team of engineers is working to create a new concrete mix that could significantly cut carbon emissions at a much faster rate.

“We can’t wait decades for concrete to absorb the carbon dioxide produced in its manufacturing process,” Mirian Velay-Lizancos, assistant professor of civil engineering, said in a news release. “We’re not trying to change the way we use concrete; we’re making the concrete work for us.”

The innovation

The team is testing adding small amounts of nanoscale titanium dioxide to concrete. Titanium dioxide is a powdery substance that is often used in sunscreen, makeup, paint, plastic, and food preservatives. 

The engineers initially tried adding the substance to concrete to improve its strength, but they noticed that something else happened with their samples. Changing the microstructure of the cement paste made the concrete more reactive to carbon dioxide. Adding even a small amount of titanium dioxide nearly doubles concrete’s natural ability to absorb CO2 from the air.

The benefits

Because concrete is so widely used, even a small carbon absorption improvement could have huge effects globally. But the engineers say this innovation could improve localized carbon absorption to such a large degree that the global effects would be massive.

“My team is making the concrete itself absorb carbon dioxide faster and in greater volumes,” Velay-Lizancos said. “We are living in a building environment. … There is no doubt that improving the sustainability of concrete, the most used construction material in the world, would mean a giant leap for sustainable development.”

The titanium dioxide also makes the concrete more durable, so it lasts longer before needing emissions-intensive replacement.