Rheological properties and group chemical composition of oxidized bitumen in the presence of fibrous materials of various structures

The rheological properties of oxidized bitumen in the presence of fibrous materials based on cellulose and chrysotile asbestos used as stabilizing additives in the production of crushed stone-mastic asphalt concrete mixtures have been studied. It has been established that the supramolecular structure of fibers characterizing the interaction between macromolecules largely determines the effectiveness of their structuring action for oxidized bitumen. Thus, the introduction of cellulose fiber leads to an increase in the ability of the bitumen colloidal structure to the simultaneous occurrence of elastic and plastic components of deformation. This is due to the uniform distribution of the fiber in the dispersion medium of bitumen due to the penetration of hydrocarbon components of bitumen into the interfibrillary space of cellulose and the rupture of hydrogen bonds between hydroxyl groups. Тhe presence of strong structural bonds between chrysotile-asbestos macromolecules prevents the formation of strong reinforcing mesh in bitumen oils. As a result, the values of the structural and rheological parameters Pk1, Pk2 and Pm of the bitumen/chrysotile-asbestos composition are 1.5–2 times lower compared to the values for the bitumen/cellulose composition. The results of the study of the group composition and structural-rheological properties of bitumen compositions after heating at T = 163 °C indicate a higher stability of the bitumen-cellulose structure to the processes of thermal oxidative degradation compared to the structure formed in the bitumen/chrysotile-asbestos composition. By the method of thin-layer chromatography, it was found that the concentration of oils in the bitumen/chrysotile-asbestos composition is higher as compared to the bitumen/cellulose composition, indicating that the weakening of rheological properties and thermal stability in the presence of chrysotile-asbestos is not related to the microstructure of its fibers, which, according to some researchers, is prone to selective diffusion of oils into the capillaries of fibrils.