Impact of Freeze–Thaw Cycles on Mechanical Properties of Asphalt Mixes

This study presented a statistical assessment of the impact of freeze–thaw cycles on deterioration of the mechanistic properties of asphalt mixes. The experimental matrix included several samples of asphalt mixes that were tested with dynamic modulus. The specimens were retested after being subjected to freeze–thaw cycles to simulate the impacts of the Canadian climate on asphalt mixes. The Ministry of Transportation of Ontario constructed a test section in partnership with the University of Waterloo, the Ontario Hot Mix Producers Association, the Natural Sciences and Engineering Research Council of Canada, and other partners to evaluate the use of perpetual flexible pavement design in southern Ontario, Canada. The test section was constructed on Highway 401, and samples from several asphalt mixes used in construction were structurally evaluated through dynamic modulus testing shortly after construction. The samples were then subjected to freeze–thaw cycles and retested to evaluate the environmental impact on dynamic modulus (| E * |) as a representative of pavement structural deterioration. The dynamic modulus results were used to evaluate the benefits obtained by adding 0.8% of additional binder to the regular Superpave ® (SP) 25 mix to develop an SP 25 rich bottom mix (RBM). The dynamic modulus results did not show a statistically significant difference between the average | E * | of the SP 25 and SP 25 RBM after construction. However, the benefits of additional binder content showed up clearly after freeze–thaw cycles simulating 1 year in service. Overall, the study provided guidance on perpetual pavement design and the various asphalt layer performances within the design.