The world’s reliance on concrete, the second most consumed material after water, is resulting in an environmental and resource crisis, with sand mining rates outstripping natural replenishment.
A study by Rice University researchers found that graphene derived from metallurgical coke, a coal-based product, could serve not only as a reinforcing additive in cement but in addition as a substitute for sand in concrete.
“This might have a serious impact on one in all the largest industries on the earth,” said James Tour, Rice’s T. T. and W. F. Chao Professor and a professor of chemistry, materials science and nanoengineering. “We compared concrete made using the graphene aggregate substitute with concrete made using suitable sand aggregates, and we found our concrete is 25% lighter but just as tough.”
Concrete, a mix of aggregates like sand and gravel bonded with cement and water, is crucial for urban development. With 68% of the worldwide population expected to live in urban areas by 2050, demand for concrete and hence sand mining is projected to grow significantly. This has tripled within the last twenty years, reaching about 50 billion tons yearly. Nevertheless, this comes at a major environmental cost.
Cement production, a key component of concrete, accounts for 8% of worldwide carbon dioxide emissions. Furthermore, sand mining, largely unregulated, poses severe threats to river and coastal ecosystems. Based on a 2022 United Nations report, this escalating demand for sand, coupled with population growth and concrete expansion, could soon trigger a “sand crisis.”
Applying its signature Joule-heating technique to metallurgical coke, the Tour lab has created a style of graphene that would function an alternative choice to sand in concrete.
“Initial experiments where metallurgical coke was converted into graphene resulted in a cloth that appeared similar in size to sand,” said Paul Advincula, a Rice doctoral alum who’s a lead creator on the study. “We decided to explore using metallurgical coke-derived graphene as a complete substitute for sand in concrete, and our findings show that it could work rather well.”
Tests comparing conventional concrete with concrete constructed from graphene aggregates show promising results. The graphene-based concrete not only matches the mechanical properties of ordinary concrete but in addition offers the next strength-to-weight ratio.
The Tour lab has used Flash Joule heating for quite a lot of applications, including hybrid carbon nanomaterials synthesis, battery part recycling and heavy metal removal from coal fly ash.
“This system produces graphene faster and at a bigger scale than previous methods,” Advincula said.
With the potential to scale back reliance on natural sand and lower carbon emissions from the concrete industry, this latest technology could lead on to more sustainable urban development practices.
“It is going to take a while for the value of graphene to get low enough to make this viable,” Tour said. “But this just shows there are alternatives we are able to pursue.”
Satish Nagarajaiah, a professor of civil and environmental engineering and of mechanical engineering who’s a corresponding creator on the study, emphasized that “30% of concrete consists of sand — a major part.”
“The indisputable fact that we’re getting ready to a ‘sand crisis’ motivates us to search for alternatives, and metallurgical coke, which costs in regards to the same as sand at about 10% of the fee of concrete, could help not only make better-quality concrete, but in addition eventually translate into significant savings,” Nagarajaiah said.
The research was supported by the U.S. Army Corps of Engineers, Engineer Research and Development Center (W912HZ-21-2-0050), the Air Force Office of Scientific Research (FA9550-22-1-0526) and the National Science Foundation.
