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Rice University researchers have found that graphene derived from metallurgical coke, a coal-based product, could serve not only as a reinforcing additive in cement but also as a replacement for sand in concrete.
To develop their special graphene, the scientists applied a Joule-heating technique to metallurgical coke.
“Initial experiments where metallurgical coke was converted into graphene resulted in a material that appeared similar in size to sand,” said Paul Advincula, lead author of the study published in Applied Materials & Interfaces. “We decided to explore the use of metallurgical coke-derived graphene as a total replacement for sand in concrete, and our findings show that it would work really well.”
The scientists compared concrete made using the graphene aggregate substitute with concrete made using suitable sand aggregates and discovered that their concrete is 25% lighter but just as tough. In other words, the graphene-based concrete matches the mechanical properties of standard concrete and offers a higher strength-to-weight ratio.
Advincula noted that the ‘flash Joule heating‘ technique produces graphene faster and at a larger scale than previous methods.
With the potential to reduce reliance on natural sand and lower carbon emissions from the concrete industry, the researcher believes this new technology could lead to more sustainable urban development practices.
“It will take some time for the price of graphene to get low enough to make this viable,” head researcher James Tour said. “But this just shows there are alternatives we can pursue.”
Tour pointed out that with 68% of the global population expected to live in urban areas by 2050, demand for concrete and, hence, sand mining is projected to grow significantly. This has tripled in the last two decades, reaching about 50 billion tons yearly, and comes at a significant environmental cost.
In addition, cement production, a key component of concrete, accounts for 8% of worldwide carbon dioxide emissions. Moreover, sand mining, largely unregulated, poses severe threats to river and coastal ecosystems. According to a 2022 United Nations report, this escalating demand for sand, coupled with population growth and urban expansion, could soon trigger a “sand crisis.”
“The fact that we’re on the brink of a ‘sand crisis’ motivates us to look for alternatives, and metallurgical coke, which costs about the same as sand at about 10% of the cost of concrete, could help not only make better-quality concrete but also eventually translate into significant savings,” Satish Nagarajaiah, a professor of civil and environmental engineering who is a corresponding author on the paper, said.
