Rice University researchers have devised a new method for converting used tires into graphene, and it can be used to create concrete. The team claims that the concrete mixture is much stronger as well as being more eco-friendly.
In 2020, the team illustrated the technique using waste materials such as food and plastic, and they've already switched on to recycled tires. According to the Rice team, previous attempts to transform tires directly into graphene didn't produce the best results, so they switched to the stuff left over after they had gone through a standard recycling method for the latest research. The research expanded on the team's past success in producing graphene using a technique known as flash Joule heating. This means, rapidly superheating about every carbon source over 2,725 °C (4,940 °F) and transforming it to graphene flakes using a jolt of electricity.
This tire-derived carbon black proved to be an excellent candidate for producing flash graphene, according to the Rice researchers. Pyrolysis is the process of burning tires in a low-oxygen atmosphere to produce an oil that can be used in a number of industrial processes. However, it leaves a strong carbon residue that has become more difficult to repurpose. The team then illustrated a specific application of the new graphene material: cement processing. They added 0.1 weight percent (wt percent) of graphene made from tire carbon black to Portland cement, and 0.05 wt percent of carbon black and shredded rubber to the combination. Concrete cylinders manufactured with this cement had a 30 percent greater compressive strength over concrete without any of the graphene compound, according to the researchers.
“This strength gain is due in part to a seeding effect of 2D graphene for higher growth of cement hydrate materials, and in part to a strength properties at later stages,” states study co-lead author Rouzbeh Shahsavari.