Experimental study on asphalt mixture recovery

Abstract

Asphalt materials used in road pavements are exposed to repeated heavy traffic loading under changing climates. These phenomena make pavements prone to fatigue deterioration as a consequence of the formation of micro-cracks, which can coalesce into a network, ultimately leading to macro cracking and structural collapse. Susceptibility of asphalt mixtures to fatigue is usually evaluated through cyclic laboratory testing, where asphalt specimens are subjected to sinusoidal loading cycles. As the number of cycles increases, a significant loss in material stiffness occurs. However, if loading is interrupted by introducing a rest period between two continuous loading phases, an important change in material behavior is observed. This is associated with a substantial stiffness recovery, which in turn triggers the material’s fatigue life. In this study, the phenomenon of stiffness recovery during rest periods is investigated. Cyclic uniaxial tension–compression loading tests are conducted in stress-control mode and rest periods of different durations are considered. Dissipated energy is analyzed and used to assess the material’s capability for recovery and a new recovery index is proposed. It is found that the newly developed index can successfully assess the recovery properties of asphalt mixture.