A distinctive feature of composites is the manifestation of a synergistic effect due to the interaction of contacting substances at the interphase layer, and their intensity of interaction affects the volume properties of the composites. A study of the interphase layer of bitumen was carried out on the surface of the mineral powder. The proposed method according to the results of rheological tests allows calculating the thickness of the boundary layer in the binary system “asphalt – dispersed phase”. The dependence of the road composite strength on the layer thickness of structured asphalt is established: the strength of the composite increases with increasing thickness of the bitumen layer. Method of assessing the impact on the structural-sensitive properties of the composite extensive factor m – indicator reflecting the influence of the interface area and intensive factor n – indicator reflecting the influence of physicochemical effects at the interface is proposed. The extensive factor has a greater effect on the properties of SMA-20 with a quartz filler m/n > 2. There is a higher rate of decrease in the intensity of physicochemical interactions at the interface of the «oil bitumen-silica filler» phase as compared with the extensive factor. The different nature of the effect of temperature on the extensive and intensive factors is observed for SMA-20 with diatomite: as temperature increases, the factor m increases, whereas the opposite effect is observed for factor n. It indicates a positive effect of the specific surface of diatomite on the temperature properties of asphalt concrete.