The AASHTOWare Pavement ME Design (PMED) software is a comprehensive design and analysis tool, which can predict different types of distresses in pavements for various design inputs. Asphalt binder grades or properties is one of the key inputs into software for the design and analysis of flexible pavements. The TAC ME Pavement Design Subcommittee conducted several design trials to evaluate the impact of nine different asphalt binder grades (PG 52 to PG 70 and PG-28 to PG-40) on the predicted distresses in 11 different climatic areas across Canada. The aim of these design trials was to assess the impacts of varied asphalt binder performance grade (PG) on the predicted distresses including their trends and practical significance.
The analyses of trial results indicated that softer binders in terms of reduced low temperature grades, reduce the predicted thermal cracking (TC) in some climatic areas. Increased high temperature grades, with no change in low temperature grade, generally result in reduction of thermal cracks, which seem to be unreasonable. The predicted rut depths in asphalt concrete (AC) layer increase with reduced low temperature grades and reduce with increased high temperature grades, as expected. The predicted bottom-up fatigue cracking (BUFC) and top-down fatigue cracking (TDFC) increase with reduced low temperature grades, and they also reduce with increased high temperature grades, which are unexpected. Some inconsistencies in predicted distresses among the climatic areas were also observed. The mean or maximum air temperatures are statistically significant variables for BUFC and TDFC with logical trends. However, the sensitivity of climatic conditions on the predicted TDFC was low. The PMED software predicted surface smoothness, in terms of international roughness index (IRI), mostly depended on the predicted rutting and cracking. This paper presents the details of these trial results, analyses and findings.