Analysis of shear-torque fatigue test for bituminous pavement interlayers

The laboratory characterisation of bituminous interlayers is a challenging issue because of the difficulty of establishing loading conditions that can simulate field behaviour. This paper describes a shear-torque fatigue test procedure aimed at investigating the fatigue behaviour of bituminous pavement interlayers. A preliminary experimental investigation, able to evaluate the damage process occurring in both single- and double-layered specimens, showed that the presence of the interface constitutes a weakness zone, noticeably influencing the shear fatigue performance of the pavement structure. Thus, a model for the description of the evolution of the interlayer damage by using the variation of the interlayer complex shear modulus was proposed and preliminarily validated. Moreover, a new fatigue failure criterion has been proposed to be used in the result analysis of the shear-torque fatigue tests.