Researchers have sharpened a process of converting old rubber into graphene. The material can make concrete significantly stronger, which also provides environmental benefits.
Concrete structures are one of the biggest environmental problems – or rather the production of the cement that is included in the building material. According to Rice University, cement production can account for 9 percent of the earth’s carbon dioxide emissions from human activities.
China is a leader in the field – in a negative sense. There, cement production emitted 823 million tonnes of carbon dioxide in 2019, according to Statista. But countries such as Vietnam and Indonesia also have sharply increasing emissions from cement production.
According to the industry itself About 60 percent of the emissions in production come from the process itself, and the remaining carbon dioxide comes from the fossil fuels used. There is a lot of work going on to find materials that can strengthen the concrete and thus open up for a reduced proportion of cement. The latest example comes from Rice University.
Waste from old tires can already be included in ordinary Portland cement today, but researchers in Houston have now optimized a process where the rubber is converted to graphene, which can make concrete stronger at the molecular level. writes Rice University.
The process converts 70 percent to graphene
Chemist James Tour and his colleagues developed what they call the flash process in 2020. With it, the team has transformed food waste and plastic into pure carbon particles with the help of a short and powerful electrical pulse – of 300 milliseconds to 1 second.
Everything else disappears, and the remaining atoms happen to resemble turbostratic graphene, which due to its structure is more soluble than the graphene produced via exfoliation of graphite. This turbostratically makes graphene a better composite material. The problem with the original, however, is the high price. But the electricity cost to produce the new material is only about 100 dollars per ton.
With the flash process, Rice can convert up to 70 percent of the rubber into graphene. It turned out to be a little more complicated to carry out with old rubber than other waste, but sharpening the process was well worth it. For the tires were previously rather useless after they had been extracted from their oils, and therefore there is a huge range available – more precisely 800 million tires a year.
How much stronger can the researchers’ graph then make the concrete? Rice tested a mixture of 0.05 to 0.1% by weight, and after seven days with the higher proportion, the test cylinder of Portland cement had at least 30% higher compressive strength. The same results were obtained with the lower mixing and 28 days curing.