This study focusses on examining the behaviour of an innovative asphalt pavement which is created as a solar energy collector, using nondestructive testing involving groundpenetrating radar. The concept of heat exchanger is based on the use of drainage asphalt in the bonding layer through which a heated fluid flows via gravity to deice the roadway. In order to develop hydrothermal models for a test site representing such a pavement, the saturated porous layer assumption was required when the water level in each tank (up and downstream of the structure) was same as the top of the porous layer. Two groundpenetrating radar techniques were tested at this test site: a groundcoupled impulse radar and an aircoupled steppedfrequency radar. The impulse groundpenetrating radar, a highefficiency nondestructive testing technique which is widely used in civil engineering, provides accurate geometric information, especially for pavement investigation. In the second innovative approach, aircoupled steppedfrequency radar was combined with fullwaveform inversion to obtain quantitative information, while retrieving the electromagnetic properties of the successive pavement layers. We concentrated on the earlystage water imbibition in the pavement structure using the impulse groundpenetrating radar to estimate the fluid transfer velocity and both groundpenetrating radar techniques to verify the saturated porous layer assumption in the steady state. Groundcoupled radar enabled us to follow the water front and to capture different watertransfer behaviours in the porous asphalt layer. Our observation could be explained by the vertical topology of the upper watertight interface. Aircoupled steppedfrequency groundpenetrating radar presented similar results to groundcoupled groundpenetrating radar but provided a quantitative estimate of the changes within the porous layer during the test.