Mechanistic design of foamed bitumen stabilised pavement bases

Foamed bitumen stabilised (FBS) materials as non-continuously bound pavement layers are being increasingly used globally in both new road pavement base construction and rehabilitation of degraded pavements. However, the essential research on testing and design methods of FBS materials is still far from complete. In current pavement design practice, the laboratory-derived fatigue criterion of asphalt is used directly for FBS materials. This paper critically discusses the limitations in current pavement design and test methods and proposes a detailed bottom-up study for the characterisation of the flexural fatigue behaviour of FBS materials under both laboratory and field conditions. The numerical results obtained from Circly computer program revealed that the critical pavement response under standard axle loading is below the inner wheel of the standard axle along the vehicle travel direction. The analysis of numerical results showed that the level of interaction between the axles of various axle configurations increases with increasing FBS base layer thickness. Moreover, the ratio of the maximum compressive stress divided by the maximum tensile stress (R) at bottom of the FBS base under standard axle loading was determined to be less than 10% for all the FBS base layer thicknesses employed in this study.