The structure and properties of active powder of discretely devulcanized rubber (APDDR) produced by the technique of high-temperature shear-induced grinding in rotary dispergators is studied. The morphology of APDDR particles, including such particles after mixing with hot bitumen, is examined by electron and atomic force microscopy. Rheological tests of rubber-modified bitumens demonstrate the efficiency of APDDR particles as an efficient modifier of bitumen binders and asphalt concrete pavements intended for service in different climatic zones under extreme loadings. The data are confirmed by field tests of modified asphalt concretes.

For the first time, by atomic force microscopy (AFM) methods, micro- and nanofragments of micronized powder elastomeric modifier (PEM) formed at the short-term (3 min at 160 °C) interaction of PEM with hot bitumen have been demonstrated. It is the technology of high-temperature shear-induced grinding of a worn-out tire’s crumb rubber or its co-grinding with styrene–butadiene–styrene (SBS) block copolymer which provides the creation of the PEM structure inclined to rapid degradation in hot bitumen. The formation just after the preparation process of a new structure of a modified binder, more resistant to external effects, is supported by the data of rheological tests. Performance tests for a modified binder using Superpave standard adopted by the road industry for bituminous binders showed an extended temperature range, resistance to rutting, and low-temperature and fatigue cracking. The better resistance to low-temperature and fatigue cracking is certainly related to energy absorption and crack growth stopping in the presence of micron and submicron resilient PEM fragments in accordance with the mechanism of increasing impact toughness in plastics.

Structural features of crumb rubber (CR) particles obtained by grinding on rollers and ultra-disperse powder elastomeric modifiers (PEM) obtained by high-temperature shear-induced grinding (HTSG) of CR or co-grinding with butadiene styrene thermoplastic elastomer (SBS) have been studied by electron and optical microscopy methods. Samples of modified bitumen were obtained at different mixing times (1–40 min) in a wide temperature range (120–180 °C). The products of interaction of PEM with hot bitumen precipitated on filters when washed with solvent from modified bitumen (MB) were studied by scanning electron microscopy (SEM). The self-similarity PEM particles and PEM breakdown fragments in bitumen up to the size of 100–200 nm were noted. The rapid (for 1 min) decomposition of PEM particles into fragments is shown, which is due to the specific structure formed as a result of HTSG. It has been suggested that this fragmentation may be caused by bitumen penetrating deep into the porous particle and breaking it, due to differently directed swelling pressure and precede the classical swelling associated with the penetration of solvent between rubber macromolecules, or occur concurrently with it.

To evaluate the effectiveness of asphalt–concrete powder modifiers (PMs) prepared via high-temperature shear-induced grinding of waste tire rubber or its cogrinding with thermoplastic elastomers and employed according to the Russian dry process, regulatory requirements to the model binder were specified. The process of evaluation of the optimal concentration of PMs in model binder (MB), which improves the rheological characteristics in the entire temperature range in service of road pavement, is shown. It is determined that fatigue tests of MBs are decisive in the determination of optimal concentration of PMs. A decrease in the concentration of PM below optimal could worsen the stability of MB to the formation of fatigue cracks as compared to initial bitumen. The suggested set of tests can be recommended for the choice of the composition and evaluation of the quality of rubber–bitumen and polymer–bitumen binders.

The flow curves are plotted and analyzed for bitumen composites modified with tire rubber vulcanizates obtained via high-temperature shear-induced grinding and with butadiene styrene thermoelastoplastics of domestic and foreign manufacture. The efficiency of ground vulcanizates and thermoelastoplastics manifests itself at their various ratios in a bitumen/modifier system, which is due to the different mechanisms of their modifying effect. Two ranges in the flow curves of modified bitumen composites have been distinguished that are associated with peculiar regularities of the structural formation at various bitumen/modifier ratios and the modifier nature. Thus, the modifier content leading to the appearance of two pronounced ranges in the viscosity curves can be considered as an efficient concentration serving as an indicator of the beginning of the modifying effect of thermoelastoplastics and ground vulcanizates.