This report documents a project to develop a new laboratory fatigue relationship to predict the performance of foamed bitumen stabilised (FBS) materials.
The project focused on extensive laboratory experiments including indirect tensile testing and flexural testing to determine the modulus, strength, and fatigue characteristics of FBS samples prepared and cured in the laboratory (cylinders and beams). A comprehensive testing program and procedures to measure and analyse the fatigue life of FBS materials were developed. Five different host materials were selected for the laboratory investigation including three crushed rocks and two recycled blends (i.e. reclaimed asphalt pavement and previously cement-treated material).
The fatigue relationships were derived for each individual mix using strain‑based and stress-based analyses. The results showed that the average strain damage exponent of the tested mixes is 7.8 and suggested that a combination of different properties that were found to be correlated to fatigue performance can provide a means of predicting the fatigue life for different FBS mixes.
New laboratory fatigue relationships were developed for the FBS materials using regression analysis of a wide range of data obtained from different phases of the laboratory testing. The fatigue lives of the mixes were then predicted using the developed models. The predictions using the strain-based relationship showed a generally acceptable conformity with the laboratory-measured data. A slightly lower prediction quality was found for the stress-based relationship. However, the predicted life from the stress-based analysis was still in reasonable agreement with the FBS measured fatigue life with limited exceptions. The report can be downloaded from Austroads at https://austroads.com.au/publications/pavement/ap-r666-22