In-situ Accelerated Testing of Bituminous Mixtures

The in-service behaviour of a standard Irish Dense Base Coarse Macadam mixture (DBC) was evaluated by using the material to overlay a road section, which was based upon a weak pavement structure. The response of the layer under a fully laden dual axle truck was examined using a series of pressure cells and asphalt strain gauges that were embedded in the test section. The section was traversed repeatedly until a network of fatigue cracks was observed on the road surface. The transverse horizontal tensile strain was found to be the most critical parameter with respect to crack initiation. When based on in-situ measured strain data, the analytical model that was developed to predict pavement performance on the basis of fundamental laboratory test data, was found to underestimate the in-service fatigue life of the DBC mixture by a factor of 13.5. The underestimation may be attributed to factors that are not accounted for in the analytical models such as material healing, traffic wander and in-situ environmental , which possibly lead to lower fatigue estimates.