Case study of detection of artificial defects in an experimental pavement structure using 3D GPR systems

Over the past years, radar systems have emerged as a powerful non-destructive testing (NDT) technique for pavement surveys. Radar systems have several major advantages, such as a high data acquisition rate and global monitoring through quasi-continuous measurements. Two radar techniques are tested for pavement structures. Impulse radar was the first technology used by the GPR community. In the 1990s, step-frequency technology enabled larger bandwidth and improved time resolution. The two radar techniques are now able to collect data at traffic speed. They record measurements along a longitudinal profile usually located in a wheel-path to provide Bscan records of the roadways pavement. It allows to detect layer interfaces and to estimate layer thickness and sometimes to detect internal defects such as sliding the interface. Since few years, new radar systems have been developed to record several longitudinal profiles and retrieve the 3D view of the pavement structure. In 2013, the opportunity has been found to record some GPR data on the accelerated pavement testing facility of IFSTTAR, with some exhibitors of GPR equipment during the IWAGPR workshop in Nantes. The paper presents the results obtained with two such systems. The results are compared with those from classical GPR on a qualitative basis. The contribution of 3D GPR is clearly demonstrated to detect the spatial extension of pavement layer debonding.