Reinventing Cement to Build a Greener Future

Engineers at the University of Massachusetts Amherst have received a four-year, $3 million award from the National Science Foundation’s Future Manufacturing Program to take the process of cement making out of the 19th century and into the 21st.

Ordinary Portland cement is the most ubiquitous man-made building material—and it comes with a massive carbon footprint. 

“People estimate that generating 1 ton of cement will generate about 1 ton of CO₂,” says Guoping Zhang, professor of civil and environmental engineering and principal investigator of the research. “As a result, cement manufacturing accounts for 8% of total anthropogenic CO₂ emissions in 2018, which include fossil fuels, heating, food production, everything. So that’s a lot.” 

“We want to invert two processes,” explains Zhang. “One is the traditional Portland cement manufacturing process to combat the CO₂ emissions—even to store and use the CO₂ in the next-generation cement.” 

The current process of making cement has been around since 1824, for exactly two centuries. Limestone and clay are fired to 1,450° Celsius, which requires great energy input and releases huge amounts of carbon dioxide. Only a tiny fraction of it is re-adsorbed during curing via a process called carbonation or carbon mineralization. These fired materials are then pulverized into a powder. The heating and grinding processes are also heavily energy-intensive processes with large carbon footprints.

Second, the researchers see an opportunity to divert the waste stream that comes from mining metals for electric vehicles and energy storage and repurpose these mine residues to make cement. 

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“You need to extract minerals from the ground to make a huge volume of these metals for wind and solar energy production and making batteries for energy storage so the demand is just going to increase over time,” says Peng Bai, assistant professor of chemical engineering. “If we don’t use them, these mine tailings are just waste. At the same time, they contain ingredients that can be used for other processes.” In the case of inverted cement, that waste contains calcium, magnesium, iron and silicon. 

In their proposed new method, captured and atmospheric carbon dioxide reacts with the calcium, iron and magnesium to grow into nanoscale carbonate crystals, using the original rock-stored silicon oxide chains and sheets as a scaffolding to hold the strong nano carbonates. This thermodynamically favored process effectively pulls carbon out of the air and stores it as a strong solid, which is expected to do a better job than the current ordinary Portland cement.

“We have hints from literature and our previous work that individual parts of this process should work but there is also a lot of exploratory research to be done to really make this an actual manufacturing process so it’s very exciting,” Peng adds.

This award also involves collaboration with other four academic institutions across the country, including Worcester Polytechnic Institute, University of California San Diego, University of Alabama, and Southern University, and has an intensive education and outreach plan to train next-generation workforce with diverse skills including future manufacturing, circular economy, sustainability, and construction materials.