Investigating High-Temperature PG Grade Adjustment Recommendations for Airfield Pavements

This study aims to investigate the high-temperature performance grade (PG) adjustment (bumping) recommendations included in various international specifications and guidelines for airfield pavements, particularly for asphalt intermediate and base layers. The research was instigated following recent asphalt rutting occurrences in airport pavements. Mechanistic analysis, using the software FlexPave (TM), was employed to assess airfield pavement responses under hot climatic conditions and for different loading conditions. The results of the analysis pointed to three important factors that should be considered when selecting binder PG grades for airfield pavements, particularly for the asphalt intermediate and base layers: (1) deeper layers within an airfield pavement structure are subjected to considerably high compressive stresses; (2) deeper layers within an airfield pavement structure are subjected to longer loading times compared with surface layers; and (3) deeper layers within a pavement structure experience consistently high temperatures. Therefore, it is recommended that PG grade bumping be applied beyond the surface layer in airfield pavements, to the intermediate and base layers, in locations that experience very high temperatures and where rutting is a critical distress. This recommendation was supported by two case studies of airfield pavements in hot climates, where the one that applied PG grade bumping for the base layer performed well under heavy loading, while the one that did not apply PG grade bumping experienced premature rutting failure.