Pavement

The Austroads asphalt pavement design process set out in Guide to Pavement Technology – Part 2: Pavement Structural Design (Austroads 2008) utilises a mechanistic procedure to predict the allowable traffic repetitions until asphalt fatigue occurs. With the current fatigue based design approach, asphalt design thickness will continue to increase in the future due to ever increasing traffic loadings and the low asphalt stiffness achieved in many areas of Australia (due to warm climate). Asphalt thicknesses for some recently designed heavy duty full depth asphalt pavements in Australia have exceeded 500 mm.Researchers have postulated that an asphalt fatigue endurance limit exists where applied strain is sufficiently low no damage occurs. The premise being that the rate of asphalt healing exceeds the rate of damage accumulation, being fatigue cracking at the base of the asphalt pavement. The corresponding thickness would provide a limit for the pavement where additional asphalt thickness provides no additional benefit to fatigue life and represents an unneeded expense (Carpenter et al. 2003). Similar concepts have been identified for other materials, including metals and concrete pavements, and are now commonly incorporated into design methods for these materials.