When you think of resources we’re running out of, sand might not be high on your list, but it’s up there thanks to our high demand for concrete. Scientists at Rice University have now shown that substituting graphene can not only save sand, but makes concrete lighter, stronger and tougher.
Despite being a sheet of carbon atoms just one atom thick, graphene has a reputation for being incredibly strong. As such, it’s no surprise that this ‘wonder material’ has been mixed into concrete before, usually to make it stronger and more durable. But that usually involves just adding graphene to the recipe – for the new study, the Rice team wanted to replace sand completely.
Concrete is made of three main ingredients: water, an aggregate like sand, and cement to bind it all together. Sand is the largest component by volume, and given modern humanity’s insatiable appetite for concrete, sand mining is increasing. Not only is this process destructive, but it risks running out of sources.
The research comes from the lab of Rice University chemist James Tour, whose team has been making graphene for years using a technique they developed called flash Joule heating. Essentially, a carbon-rich base material is quickly superheated with a zap of electricity, converting it into graphene flakes. In this case, the base material was metallurgical coke, a fuel source created from coal.
“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. “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.”
Saving sand wasn’t the only benefit, either. The resulting concrete was 25% lighter than concrete made with a normal aggregate, and showed a 32% increase in toughness, 33% in peak strain, and 21% in compressive strength. On the down side, there was an 11% reduction in its Young’s modulus, a measure of a material’s resistance to deformation by stretching.
While the team says graphene is currently too expensive to make this method commercially viable at scale, it at least shows that there are alternatives that could be pursued.
Concrete is made of three main ingredients: water, an aggregate like sand, and cement to bind it all together. Sand is the largest component by volume, and given modern humanity’s insatiable appetite for concrete, sand mining is increasing. Not only is this process destructive, but it risks running out of sources.