Rheological Properties of Bitumen with Powder Rubber Modifier Obtained by High-Temperature Shear Grinding

The influence on the rheological properties of bitumen of the powder rubber modifier (PRM), based on active powder of discretely devulcanized rubber (APDDR) has been investigated. APDDR obtained by the method of High-Temperature Shear Grinding from the Crumb Rubber of waste tire. A specific feature of APDDR is its rapid decay into micro- and nano-fragments upon contact with hot bitumen, which allows using PRM during mixing asphalt concrete without changing the temperature and time conditions for preparing the mixture. The change in the structure of the binder upon addition of PRM to bitumen is shown by AFM-spectroscopy and by the example of the change in the complex viscosity: at high temperatures it is higher, but starting from a certain temperature, the position of which depends on the thermo-history of the sample, the complex viscosity decreases in comparison with the bitumen. The phenomenon of dynamic glass transition (DGT) at low temperatures observed in bitumen in the frequency range corresponding to vehicles speed is investigated. It is shown that DGT is absent in modified bitumen at the optimum concentration of PRM. The improvement in the fatigue properties of bitumen as a result of modification of the PRM is confirmed both by a decrease in the value of the loss modulus and by the introduced parameter - the fracture temperature during cyclic tests. This temperature corresponds to the sharp cracking of the sample, which occurs during cyclic tests with an increase in strain from 0.1 to 5%, when the loss modulus reaches 25 MPa.