Experimental Measurements of Interfacial Mechanical Properties between Rehabilitated Bituminous Layers Using Innovative Approaches

Bituminous pavements frequently fail at an early age well below the predicted design life, which in turn necessitates taking rehabilitation actions to recover the serviceability to an acceptable level for users. Two rehabilitation techniques have been the focus of the engineering community: a traditional method known as the mill and fill and the other, which attracts increasing interest, is to take advantage of an interlayer before resurfacing. This rehabilitation technique is more challenging from the theoretical point of view since the traditional test methods need to be adapted to capture the mechanical properties that, in the presence of the interlayer, may emerge. On this ground, the focus of this paper is to gain an in-depth understanding of mechanical properties developed at the interface between two asphalt layers as in an unreinforced case and between a layer of paving fabric (a system composed of binder and synthetic fabric) and asphalt layers as in a reinforced case. To achieve this goal, three main properties were addressed: the antireflective property of the interface against crack propagation was examined via a modified three-point bending test (3-PBT) by calculating the J-integral and measuring the crack width below and above the interface. Besides, the stiffness properties in two perpendicular directions at the interface were separately studied through novel approaches to find out the possible mechanical effects induced by the interlayer on structural responses of a composite structure. The experimental results derived from this study revealed that the reinforced interface, including the paving fabric, had about 5 times the higher capacity in delaying the propagation of bottom-up cracking than the unreinforced one. However, this promising result was accompanied by 2.5 and 1.5 reductions in bonding quality and dynamic modulus, respectively, at the reinforced interface, which in turn necessitates introducing the real mechanical behavior of the reinforced system into design methods.