Pavements and surfacings on WA airports

Western Australia has a network of airports servicing towns, mines and oil and gas projects. These are almost totally flexible pavements. Historically they were built with naturally occurring granular materials for the basecourse and subbase courses and, if surfaced, had a bituminous seal. This was adequate for the DC-3 and Fokker F-27/F-28 aircraft in use in earlier days. The airport scene has changed in the last 10 to 15 years with the mining boom and fly-in, fly-out operations (FIFO). FIFO commuting has become common in WA, leading to a surge in air travel and an even greater surge in the number of airports. Safety and fatigue rules in the mining industry make it economical to locate jet airports as close as 60 km apart. Mining airports were initially serviced by small jet airliners, but in the last five years there has been an increase in airliner size. Common jet airliner types in use in WA are the BAe 146-200, Fokker F100, Boeing 717-200, Embraer 190, Airbus A320 and Boeing 737-800.

This paper addresses pavements and surfacings on airports in WA. The practices have derived over time and reflect in part the climate and geology of WA and in part the low traffic volumes on most WA airports. Awareness of differences in traffic, climate, geology and specific concerns like shallow water tables and weak clay subgrades is needed when considering these outside WA. The paper also highlights differences between airport and road pavements because the gap between the two widens for larger aircraft. Tyre loads and pressures of aircraft are higher than for regulation highway vehicles, but there are some offsetting factors for airport pavement performance:

• The bituminous surfacing is very wide and in the normal operation aircraft are several metres from the edge zone affected by lateral infiltration of water.
• Load repetitions are very low (commonly less than 10 per day) and fatigue life is much less of a concern for airports compared with roads.
• Sprayed seals on runways, taxiways and aprons have higher binder application rates than highways with the same size aggregate. The airport asphalt design typically uses a different grading and higher binder content when compared with normal road asphalt and is less permeable.
• There are no drive axles on aircraft and tyres in a dual pair can rotate independently.
• Grades on runways and taxiways are in the majority 1.5% or less.