Team Aims to Cut Concrete Carbon Emissions

FRIDAY, OCTOBER 27, 2023


A team of researchers at Arizona State University, with support from the National Science Foundation, is reportedly pursuing ways to lower carbon dioxide emissions involved in the cement and concrete manufacturing process.

According to a report from ASU, the team—led by Narayanan Neithalath, the Fulton Professor of Structural Materials in the School of Sustainable Engineering and the Built Environment, part of the Ira A. Fulton Schools of Engineering at ASU— is exploring new processing techniques using novel energy sources and ingredients for manufacturing cement.

“Construction is a big contributor to climate change,” said Neithalath. “There is no other material that can do all that concrete can, and since the demand for the product is not going to change and the construction industry is very comfortable with Portland cement, we must look carefully at alternate processing options for cement, to control the carbon emissions.”

About the Research

ASU’s release notes that more than 30 billion tons of concrete are used every year—making it second only to water as the most widely used material in the world.

The primary ingredient in cement—which the researchers say is the essential “manufactured” ingredient in concrete—is limestone, which when heated to about 900 degrees C converts to calcium oxide, resulting in the release of carbon dioxide, or CO2. The calcium oxide is then heated up to as much as 1,500 C, with silica and alumina sources to produce the binding component of cement known as cement clinker.

In addition to the CO2 released from limestone, fossil fuels are reportedly used to provide the high heat for the chemical conversion of calcium oxide, which also results in substantial CO2 emissions. In total, one ton of cement typically produces about 0.8 to 0.9 tons of CO2 emissions, resulting in approximately 8% of the world’s anthropogenic CO2 emissions, and about 25% of all industry carbon emissions, the researchers say.

To address these carbon emission challenges, Neithalath says the team’s research will focus on two main goals. The first involves using novel electrolytic and hybrid routes to separate lime from the limestone without producing CO2. The second involves utilizing autocatalysis, a process in which energy can be provided through renewable sources such as solar power, to create cement through a low-energy pathway.

While the team acknowledges that cement companies have made efforts to make their production plants more energy efficient, carbon dioxide is still produced from calcium carbonate and “has to go somewhere.”

Neithalath notes that the consistency of the cement produced, as well as the scalability of the production process changes, are the main challenges his team will face in its research, as they aim to avoid the costs and time involved with completely replacing existing infrastructure.

“There is no one lever to reducing concrete’s carbon emissions, but there is a general consensus that process changes in cement manufacturing could have the highest impact, though that could be the hardest thing to do,” says Neithalath.

“While this is likely feasible experimentally, these are relevant questions when it comes to large-scale production and industry adoption of what we can develop.”

Other ASU researchers involved in the project include Patrick Phelan, a professor in the School for Engineering Matter, Transport and Energy, part of the Fulton Schools; Dong-Kyun Seo, a professor in the School of Molecular Sciences; and Diana Bowman, the associate dean of applied research and engagement in the Sandra Day O’Connor College of Law at ASU. Other members of the team include Aditya Kumar, an associate professor materials science and engineering at Missouri University of Science and Technology; and Srinivas Kilambi, a chemical engineer and innovator.

The project is reportedly being funded in part by a Future Manufacturing Research Grant from the National Science Foundation.

Other Concrete Research

Earlier this year, in March, researchers at Washington University in St. Louis began developing an innovative and economical process for mineralizing carbon dioxide to produce carbon-negative concrete products.

Led by the McKelvey School of Engineering, Washington University professor Xinhua Liang was collaborating with Missouri University of Science and Technlogy professors Hongyan Ma and Manashi Nath, as well as GTI Energy Research and Development Manager Shiguang Li. The research is reportedly being conducted through a two-year, $2 million grant from the U.S. Department of Energy.

According to the university, Liang and his collaborators plan to convert carbon dioxide from point emission sources into chemicals that would be mixed with selected industrial solid wastes to create cement alternatives, which can then be used for concrete products.

The technology reportedly has the potential to reduce the cost of cement production by 27% and change the cement and concrete industries to carbon-negative, or a reduction of 1.2 gigatons of carbon dioxide emission per year with 100% use of the proposed technology.

“The cement and steel industries are big contributors of carbon dioxide emission,” Liang said. “Production of 1 ton of Portland cement emits about 0.71 tons of carbon dioxide.

“We plan to create a laboratory-scale prototype system that can convert 10 kilograms of carbon dioxide a day to make precast concrete blocks.”

Also, in April, researchers from Washington State University announced that they had developed an environmentally friendly concrete that is nearly as strong as regular concrete, using biochar and concrete wastewater.

According to the university’s release, the biochar was also able to suck up to 23% of its weight in carbon dioxide from the air. The research, led by doctoral student Zhipeng Li, was recently published in the journal Materials Letters.

While researchers have previously tried adding biochar as a substitute in cement, adding even 3% of biochar dramatically reduced the strength of the concrete. However, WSU researchers treated biochar in the concrete washout wastewater, allowing them to add up to 30% biochar to their cement mixture.

The paste made of the biochar-amended cement was reportedly able to reach a compressive strength after 28 days comparable to that of ordinary cement of about 4,000 pounds per square inch.

“We’re very excited that this will contribute to the mission of zero-carbon built environment,” said Xianming Shi, professor in the WSU Department of Civil and Environmental Engineering and the corresponding author on the paper.

The university reported they were actively seeking industry partners from the building and construction sector to scale up production for field demonstrations and licensing this WSU technology.

   

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