Lessons Learnt from Ten Years of Maintenance on Defence Aircraft Pavements in Australia

The Australian Department of Defence manages, maintains and operates twenty-four airfields around Australia. These airfields range in their size, infrastructure provisions, operational capability and environment. Over the last ten years, the management of maintenance at these airfields has uncovered unique problems, allowed trials of various maintenance approaches to be conducted and presented many opportunities to learn valuable lessons for the future. Surface enrichment of asphalt using both tar-based and bitumen-based materials has been performed on many pavements. This has proven to be an effective means of increasing the period between asphalt overlays. Such treatments require careful attention to the application rates and selection of the enrichment product. The interface between concrete and asphalt surfaced pavements presents a design challenge. If not detailed appropriately, differential thermal expansion and contraction can lead to shoving and cracking of asphalt as well as spalling of concrete. In extreme conditions, it is possible to retrofit an isolation joint to these interfaces to improve their condition. Hot bitumen sprayed seals can provide an appropriate surfacing for the operation of non-jet aircraft. While the materials and equipment are generally the same as for road pavements, the subtle design and specification differences are not commonly understood by contractors. Careful design and construction management is required to obtain the optimum sealed surface for an aircraft pavement. The repair of minor concrete spalling is likely to be required on many aircraft parking aprons. A range of materials have been trial tested with varying degrees of success. A proprietary semi-rigid epoxy has been found to be the most reliable and durable product for concrete spall repairs, with trenches of asphalt suitable for cracked slabs. Asphalt surfacings will unavoidably be segregated in isolated areas and over time aggregate will erode from the surface. Use of 14 mm asphalt surfacing, in lieu of the traditional 20 mm asphalt mix, requires grooving of the surface to achieve the required skid resistance but significantly reduces built-in segregation. Polymer modified bitumen emulsion slurries effectively treat remaining areas of segregated and eroded asphalt