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.
The research was published in the journal ACS Applied Materials.
Source: Rice University
There is plenty of sand in the Sahara, but apparently it is the 'wrong type'.
Graphene costs somewhere in the range of $20 to $2000 per kilogram. Sand costs around $0.01 per kilogram.
Replacing sand with diamond, or aluminum oxide, would probably make for stronger and/or lighter concrete as well, but this is straight up no brainer stupid.
So we have a proof of concept that cannot be feasibly produced for real world studies, for recycling, or for any other hair-brained commenter's recommendations. Maybe someone should contact Elon Musk and let him consider this material for his Rocket Launch pads - he has the money and the quirkiness to run with this type of research!
As for all the naysayers who say this process is too expensive so it shouldn't be researched, remember the story of aluminum. Once upon a time, very hard to refine, so it cost something like 60x what it does today. Then somebody figured out an economical process and today it's one of the most commonly used metals in the world. Graphene is still new. It wasn't even isolated until 20 years ago. For all you know, somebody may figure out a way to synthesize it in bulk from atmospheric carbon dioxide, making it an ideal carbon sequestration method and killing two birds with one stone.