Interpreting asphalt concrete creep behaviour through non-Newtonian mastic rheology

This paper explores the use of non-Newtonian mastic models in interpreting asphalt concrete creep behaviour. Three non-Newtonian models were considered, namely the Bingham model, the Herschel-Bulkley model and the Casson model. They were fitted to dynamic shear rheometer (DSR) strain sweep data on mastics. A total of nine mastics were included involving three asphalt mix designs and three aggregate types (hard limestone, granite, and soft limestone). A PG 76-22 binder was used for all of the mastic specimens. Unconfined creep tests were performed on the asphalt concrete mixtures that constitute the mastics using a compressive stress of 207 kPa. The mastic and asphalt concrete mixture specimens were tested at 60°C. The characteristics of the non-Newtonian mastic models (i.e. yield stress, plastic viscosity and consistency) were found to be highly dependent on mastic compositions. Furthermore, the secondary creep curves of the asphalt concrete mixture that constitute the mastics were also found to be correlated to the constants of the mastic models. The plastic viscosity and consistency explained over 75% of the observed variation in asphalt mix creep slope, while the yield stress explained approximately 50% of the observed variation in the asphalt concrete creep intercept.