Use of acoustic techniques to analyse interlayer shear-torque fatigue test in asphalt mixtures

Shear-torque tests were used for the first time to assess the fatigue behaviour of double-layered asphalt specimens. During the test, an acoustic emission (AE) technique was used to evaluate the damage process leading to failure. Results showed that the application of cyclic loading led to the decrease of the complex shear modulus, until the physical separation of the two layers. AE analysis showed that damage mostly occurred in the interlayer zone. The comparison between mechanical and AE results suggested that the damage evolution phase occurred when approaching the end of the test when the stiffness decrease was about 70%.