In the last decade, operating tire inflation pressures have risen from 250 to 310 psi for fighter aircraft. Because these higher pressures bear directly on the pavement surface, the Air Force has begun to question whether asphalt mixtures are appropriate for fighter aircraft taxiways. Accelerated full-scale traffic of simulated F-15C/D fighters on flexible and composite test sections was studied. Halfof the asphalt mixtures used for the test sections were designed with Marshall procedures and the balance with gyratory. The differences between the plastic behavior of the Marshall mixture and the stable performance of the gyratory mix were dramatic. The premature rutting of the Marshall mixture was caused by excessive asphalt for the applied traffic, which was caused by insufficient laboratory compaction during design of the mix. It was verified that the design processcan ensure resistance to rutting of asphalt mixtures by simulating the compaction of aircraft in the laboratory with the gyratory testing machine. Heavier compaction equipment will be required when the leaner mixtures needed for modern fighters are placed on airfields. On the other hand, gyratory mixtures designed for lower contact pressures will be much more easily compacted, since they will have more asphalt. The granular layers contributed about two-thirds of the total surface rutting in all the flexible test sections, Marshall and gyratory.
Samenvatting