Les exposés écrits du congrès ont été publiés dans la langue dans laquelle ils ont été soumis à l’ATC.
The specifications for asphalt concrete (AC) mixes and resulting mix designs vary among and within highway jurisdictions. The performance of each mix type depends on materials composition and quality, traffic loads, climatic exposures, etc. The AASHTOWare Pavement ME Design (PMED) software is a comprehensive tool for the design and analysis of pavement structures incorporating various design input parameters including different properties of AC mixes. In this study, design trials were completed using the PMED software v3.0 to investigate the impact of different AC mix types on the predicted distresses in new flexible pavements and the suitability of the PMED software for this impact assessment. The trials included four different AC mixes for the surface AC layer and three different AC mixes for the base AC layer from Manitoba and Ontario. This resulted in design trials for 12 combinations of AC surface and base layers. For each combination, design trials were run for 11 weather stations across Canada, which resulted in a total of 132 design runs for the investigation.
The results from this study indicated that a higher effective binder (i.e., increased VMA) content in surface layer AC mixes results in increased AC layer rutting and bottom-up fatigue cracking (BUFC). A higher density of surface AC layer mixes results in a reduced amount of AC layer rutting and BUFC. The effects of AC mix properties on the predicted top-down fatigue cracking (TDFC) and transverse cracking (TC) were inconsistent and the reason for such inconsistent variations is unclear. The properties of base layer AC mixes have no or minimal effect on the predicted distress, except for the density of base AC layer that show some effect on the predicted BUFC. The predicted total rutting followed the similar trends as the AC layer rutting. Varied climatic exposures has significant or noticeable effect on the predicted distresses. In general, a higher maximum air temperature results in increased rutting in AC layer, a higher mean air temperature results in reduced BUFC and TDFC, a colder air temperature in winter results in increased TC. The predicted International Roughness Index (IRI) depends on predicted total rutting, total fatigue cracking (BUFC plus TDFC) and TC. The freezing index and amount of precipitation have minimal effect on the predicted IRI.