The paper presents a model for the distribution of sulfur by types of states and a model for the coalescence of sulfur droplets in a sulfur-bitumen binder, as well as a model for the coalescence of sulfur droplets in a bitumen melt. The developed models well explain the mechanisms of structure formation of sulfur bitumen materials, leading to the formation of their mechanical properties, determined experimentally both for the sulfur bitumen binder and for sulfur asphalt concrete.The model of sulfur distribution by types of states demonstrates that with an increase in the sulfur content in the bituminous binder, the proportion of sulfur in a physically free state increases, which forms a dispersed phase that increases the viscosity of the binder. This leads to a natural increase in the properties of the bituminous binder with the introduction of sulfur. The sulfur droplet coalescence model demonstrates that this process is energetically favorable. The driving force of coalescence is the Laplace pressure, which increases with an increase in the size ratio of contacting sulfur droplets. Also, with an increase in the sulfur content, the probability of overcoming the interfacial film of bitumen between sulfur drops increases, which naturally increases the likelihood of the formation of spatial sulfur structures that adversely affect the crack resistance of sulfur asphalt concrete.

Keywords: sulfur, sulfur states, strength, crack resistance, sulfur-bitumen binders, sulfur-asphalt concrete, asphalt concrete, coalescence of sulfur droplets