Comparative Analysis of Asphalt Forming Processes Based on Finely Dispersed Expanded Clay Powders

The features of the structure formation of an asphalt binder modified with a highly dispersed expanded clay powder are investigated. The viscosity of the modified asphalt binder and the formation of an adsorption layer of bitumen on the surface of the particles of the mineral component at various degrees of filling in the temperature range of 100–180^oC have been studied. The effect of the impact of expanded clay powder on the adsorption activity of bitumen, the adhesive strength of bitumen with a mineral filler and on the adhesion of an asphalt binder with a mineral filler is analyzed. It was revealed that the interaction of bitumen with highly dispersed expanded clay powder significantly increases the viscosity of the asphalt binder and increases the thickness of the bitumen film on the surface of mineral particles at all process temperatures compared with standard limestone mineral powder, which is determined by the processes of selective diffusion of low-molecular hydrocarbons into the particles of expanded clay powder occurring when combined with the binder. Modification of the asphalt binder with expanded clay powder significantly increases its adsorption activity and adhesion of bitumen to mineral aggregate and adhesive strength at the interface of the «filler–bitumen» phases. This is due not only to physical interaction, but also to the presence of an increased number of active surface adsorption centers of Lewis and Brensted on the surface of expanded clay particles, which indicates the formation of chemical bonds.