Relative hysteresis as an indicator of structural condition of pavements

The paper is devoted to the experimental study of dynamic hysteresis under impact loading on the surface of flexible pavements. The relevance of the study is associated with the lack of informative indicators of the condition of pavements, which would allow for the assessment of their structural condition taking into account the mechanisms of viscoelastic deformation. A FWD PRIMAX 1500 falling weight deflectometer was used as the measuring equipment, which allows for the registration of dynamic hysteresis loops on the pavement surface under impact loading. Based on the recorded hysteresis loops, the values of dissipated energy, potential energy of deformation and relative hysteresis were determined. For the first time, the quantitative values of relative hysteresis characterizing energy absorption in different pavement layers have been determined. The regularities of change in the relative hysteresis value with increasing load transmitted by the impact loading unit have been established. It is shown that the curve of relative hysteresis change as the load increases contains two sections. A flat section, where its value is close to constant, and a section with a monotonic increase in the value of relative hysteresis, which suggests that the loads causing this monotonic increase are critical, forming a «dangerous' fracture energy in the pavement. This result can be used in the preparation of short ultimate axial loads, as well as in the development of projects for the transport of heavy loads on public roads.