Numerical and Experimental Analysis for the Interlayer Behavior of Double-Layered Asphalt Pavement Specimens

Bonding characteristics between pavement layers have an important influence on responses of pavement structures. This paper deals with this subject by analyzing the interlayer behavior of double-layered asphalt (DLA) specimens taken from an in-service motorway using a coaxial shear test (CAST) and a layer-parallel direct shear (LPDS) test. To analyze and model the influence of the interlayer condition, finite-element simulations of CAST DLA specimens were conducted. In the models, both idealized fully bonded and no-bonding assumptions were used to characterize the interlayer behavior of DLA specimens. Experimental results presented for CAST and LPDS tests demonstrate that there is a strong influence of temperature in the interlayer bonding mechanism. At lower temperatures, there is an increase on the bonding strength produced by the binder stiffening and aggregate interlocking. Further, it was observed that comparisons of CAST experimental and numerical results indicate that the interlayer can be close to the fully bonded condition at low temperatures below 20 degrees C while the interlayer, at higher temperatures, behaves between fully bonded and no-bonding idealized conditions.