Investigation of Crack Propagation in Asphalt Pavement Based on APT Result and LEFM Analysis

When reinforcing existing cracked asphalt pavements, the design and evaluation of the durability of the reinforced structure are quite different from those of a new pavement generally based on fatigue criteria deduced from stress and strain fields computed for the undamaged pavement. For the design of reinforcement solutions, the presence of cracks and their propagation must be considered explicitly. To move in this direction, the present article aims at improving the understanding of bottom-up crack propagation in asphalt pavements. Some investigations relying on the interpretation of an accelerated full-scale fatigue test are presented as well as the numerical analysis of this test through the theory of linear elastic fracture mechanics and the Paris law. The tested pavement section is composed of four layers. The two uppermost layers are made of asphalt concrete (AC) materials whose modulus and fatigue performances are different. The pavement is subjected to repeated loads applied by the Fatigue du Béton Armé Continu (FABAC) traffic simulator of the French Institute of Science and Technology for Transport, Development and Networks (IFSTTAR), and the development of cracking in the AC layers is monitored using embedded instrumentation and Falling Weight Deflectometer (FWD) test campaigns. To better control the crack pattern that develops during the fatigue test, an artificial flaw (metal angle) is purposely placed at the bottom of the AC layers (in the transverse direction to the moving loads) to localize the initiation of cracking. A bottom-up crack is supposed to grow vertically from this defect in the AC layers. This is effectively detected and followed by the experimental measurements, which are combined to model for the analysis of the test. Finally, the kinetics of crack growth deduced from the Accelerated Pavement Test (APT) results and those computed using the Paris law calibrated from fatigue tests performed in the laboratory are compared