TESTING ASPHALTS FOR SPECIAL EXPOSURES

Airfield runways are generally made using cement concrete pavements, prone to be renewed by asphalt concrete layers, but sometimes the pavement has to meet special requirements. The Department of Highway Engineering and the Institute of Thermal and Systems Engineering, TUB, cooperated in testing such special requirements. At first, heating and cooling caused by an airplane with low-mounted jet engine, applying an important heat load in preparing to take off, had been determined in field test, by means of an IR camera. Thereafter two asphalt mixes have been laboratory tested by applying 100 cycles of in-situ, thermal effects. One was a conventional AB-20 type mix, the other a highly deformation resistant plastic asphalt. Asphalt changes after heat loads have been determined in bending fatigue tests. The particularly high thermal effects were found not to be endured even by plastic asphalt mixes. On the other hand, impacts due to common airplanes are supported by conventional asphalts. Plastic asphalts have much lower bending fatigue lives, at higher building costs than for conventional asphalts. So construction of this kind of pavements would be meaningless. While alteration of operating conditions of airplanes imposing excessive heat loads would permit the use of asphalt concrete pavements in airfields