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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.

The new AASHTOWare Pavement ME design software incorporates conversion factors into its procedure to correlate the field subgrade soil resilient modulus, measured with the falling-weight deflectometer, with the laboratory equivalent modulus for use in performance prediction. The national conversion factors recommended for use with Pavement ME were determined on the basis of data obtained from the Long-Term Pavement Performance database and were not necessarily accurate for all regions and soil types. Sensitivity analysis results are presented for the effect of field-to-laboratory subgrade modulus conversion factors on the performance of three types of pavement structures in Ontario, Canada: conventional flexible, deep-strength flexible, and composite. This work included simulation of real-world case studies extracted from the Ontario provincial pavement management system (Ontario PMS2) database. Three projects were selected for this study—Highway 6, Highway 401, and Queen Elizabeth Way—all located in southwestern Ontario. Required inputs including traffic, material characteristics, and layer thickness information were extracted from PMS2 and used to set up the projects in AASHTOWare Pavement ME. The AASHTOWare Pavement ME was executed with ranges of field-to-laboratory conversion factors for different pavement types. Statistical analyses were carried out to evaluate the effect of changing conversion factors on predicted performance. Study results suggest that the predicted performance of conventional flexible pavement is significantly affected by the subgrade modulus conversion factor. However, the impact of subgrade modulus conversion factors on predicted performance is insignificant for composite and deep-strength flexible pavement sections.