Developing Rutting Mechanical Test Methods and Specifications for Flexible Airfield Pavements.

Abstract: Airfield pavements are targeted at an improved performance level, with less permanent deformation or rutting, for safety and takeoff/landing smoothness. This can be achieved by implementing new specifications for airfield pavements based on the latest state-of-the-art methodology of designing asphalt mixtures, the Balanced Mix Design (BMD). Following the implementation of BMD by various highway agencies at the local, state, and federal levels, the Federal Aviation Administration (FAA) is considering incorporating a BMD framework in their next specifications update for flexible airfield pavements as part of advisory circular 150/5370-10H. This project specifically focuses on the rutting aspect of the FAA BMD framework at the mix design stage as well as during control strip and final production. Rutting or permanent deformation is one of the major distress types in asphalt concrete (AC) pavements, especially in the case of slow moving or stacking heavy traffic coupled with high pavement temperatures. Rutting can be further exacerbated by high wheel loads and/or tire pressure, which are higher for airfield pavements as compared to highways. With the new larger and heavier generation of aircrafts, aircraft manufacturers tend to increase tire pressure in order to increase pay load or add more wheels to maintain the load limit on each wheel.
With the aim of developing rutting test specifications for airfield AC mixtures, the tasks of the project involve setting preliminary rutting test criteria (based on thorough review of literature and developed mechanistic approach), selecting representative test protocols for airfield pavements, deriving initial rutting test criteria (based on laboratory experimental plan), refining test protocols (in particular specimen conditions) for final specifications, and recommending final refinement for the set test criteria. The four main rutting mechanical tests identified by the research team as candidates for mix design and/or quality assurance (QA) during production of airfield AC pavements are: the Asphalt Pavement Analyzer (APA), Hamburg Wheel Track Test (HWTT), High Temperature Indirect Tensile Test (HT-IDT), and Ideal Rutting Test (IRT). Moreover, the rutting criteria were refined based on a thorough mechanistic analysis and modeling of actual airfield pavements under representative aircraft loading conditions. The mechanistic analysis accounted for key differences between highway and airfield pavements, including variations in load levels, tire pressure, axle configuration, and pavement structure.