Comparison of NDT methods to detect debonded interfaces

Résumé

This paper compares different Non Destructives Techniques (NDT) to detect and characterize artificial debonding and internal crack created in an experimental pavement tested on the fatigue carrousel of IFSTTAR in Nantes. The tests presented are performed on a 25 m long pavement section, consisting of 2 bituminous layers (8 cm thick base layer, and 6 cm thick wearing course), over a granular subbase. Several types of defects have been included at the interface between the two asphalt layers. Rectangular debonded areas of different size (longitudinal or transversal direction) have been created artificially, using different techniques (sand, textile, absence of tack coat). The construction has been done by a road construction company, using standard road works equipment. Different NDT, as electromagnetic techniques (ground-penetrating radar, step-frequency radar) or as mechanical techniques, from static deflection (FWD) and radius of curvature (inclinometer) measurements to dynamic methods (Ultrasonic Pulse Echo, Frequency Response Function), have been used to detect the different geometrical characteristics of the artificial defects. This allows comparing the capability of each technique to detect such damages. Some methods are selected to survey the evolution of the defects with the number of load applications.