The mechanical evolution of asphalt concrete throuout two fatigue tests is assessed by means of a non-destructive measurement technique based on P and S-wave propagation. A five-point bending test on rectangular specimens made of steel plate overlaid with an asphalt layer makes it possible to evaluate the complex behavior of asphalt layer on steel orthothropic plate. A second device is based on cylindrical cores. Both displacement sensors and wave propagation monitor damage. From ultrasonic measurements, mechanical characteristics of the material (viscoelastic modulus M*) are deduced at each instant by an inverse analysis. Then the rheological curve (M',M") is plotted and the time dependent evolution of damage is followed up. Results from displacement sensors and wave propagation are compared and provide good perspectives.