Development of a wheel tracking test for rut resistance characterisation of unbound granular materials

To assess permanent deformation of granular materials, repeated triaxial tests are currently used in Australia. A previous research project highlighted interest in using a wheel-tracking test to obtain a better agreement with field performance. A new wheel-tracker/compactor was developed and manufactured for unbound granular material characterisation. Specimen preparation procedures have been developed and assessed, with test repeatability comparable to wheel-tracking tests on asphalt. The density of the compacted slab is uniform except close to the mould sides where wall?effect leads to lower densities. A simple correction to the total mass to be compacted was implemented. The control of the moisture conditions is obtained using a membrane which stops the material drying from the top of the specimen. A comparison between deformation performance in the laboratory with previous data obtained under accelerated pavement testing exhibited differences. These differences could not be examined in detail in the project timeframe. Results show that further research should be undertaken to investigate fundamental differences in material structure that may occur between wheel-tracking samples and in-service pavement.