Nanotechnologist at RUDN University has created an asphalt modifier from old tires and rubber

Car tires can be recycled. For example, adding crumb rubber increases the life of asphalt. Typically, tires are crushed to a particle size of a few millimeters. Further grinding is too energy-intensive . However, a new method has emerged — high-temperature shear grinding. It passes with the help of a rotary disperser. The essence of his work lies in strong compression (20-30 megapascal), as a result of which the material cracks and collapses. Simultaneously, the rubber is heated to temperatures close to devulcanization. A powder is obtained, which is then sharply cooled. To increase the efficiency of the process, scientists add other polymers to the rubber.

“Among all the possible applications of crumb rubber from used tires, the most interesting is the use in the road surface. Rubber crumb as a modifier of bitumen and asphalt mixtures increases their service life and has great potential in the road industry. This combines the problems of recycling used tires and improving the durability of roads. In this way, it is possible to reduce the consumption of primary natural resources,” Alexandre Vetcher, PhD, Deputy Director of the Scientific-educational centre “Nanotechnologies”, RUDN University.

Nanotechnologists prepared crumb rubber from car tires, and then crushed it into a powder along with styrene butadiene rubber on a rotary disperser . The powder was added to hot bitumen heated to 120-180 ℃ and stirred for 1-40 minutes. This approach is called “dry” process. This means that the dry powder is added to the mixture directly during preparation, and not at a separate technological stage.

RUDN nanotechnologists studied rubber particles before and after their interaction with hot bitumen using scanning electron microscopy. Grinding together with styrene-butadiene rubber leads to the formation of externally homogeneous hybrid particles. After a minute of stirring in hot bitumen, the powder grains are split into pieces 100-200 nanometers in size. This rapid splitting is likely due to the fact that the bitumen penetrates the pores of the particles and causes swelling in different directions. With increasing mixing time in hot bitumen, complete disintegration of the particles is not observed. On the contrary, a tendency to the formation of gel -like structures is noticeable.

“Considering that one minute of mixing corresponds to the technology for producing various asphalt concrete mixtures, it can be recommended to use additive powders in a ‘dry’ way, that is, to introduce them into the asphalt concrete mixture during its production. It will be more economical. In further studies, we will conduct rheological studies of bitumen with modifiers,” Alexandre Vetcher, PhD, Deputy Director of the Scientific-educational centre “Nanotechnologies”, RUDN University.

The results are published in Polymers.