Very Thin Asphalt Concrete as Wearing Course on Main Runway at CopenhagenAirport.

In 1998 the first part, about 30.000 square m, of the main runway, 04L-22R, at Copenhagen Airport was resurfaced using a very thin asphalt layer asnew wearing course. The works included the milling off of the top 20 mm of the old wearing course and the construction of a new 20 mm thin wearing course of the type where the asphalt paving machine is spreading a thick layer of emulsion in front of the open graded asphalt concrete being paved.The rest of the runway has successively been resurfaced in the period 1999 to 2002 using the same method. The tender documents were based on the new type of specifications based primarily on functional requirements. The requirements included end-performance requirements in an eight year warranty period. During construction of the new wearing course the work was extensively controlled by the client in order to be able to evaluate the actualquality of the new pavement and in order to be able to predict the development of the performance of the pavement using the first test results as aplatform for the comparison with future measurements. For these purposes traditional laboratory test methods as well as new test methods like thin section microscopy were used. The results of this Quality Control has put Copenhagen Airport A/S into a position where it is possible to assess whether the maintenance methods and the maintenance efforts of the contractor are satisfactory or not in relation to the functional requirements of the runway. The use of this type of wearing course has resulted in expected and also unexpected advantages. The expected advantages are good friction, good roughness, no surface water and no FOD [foreign object damage]. One ofthe unexpected advantages is that compared to conventional pavements for runways almost no rubber from the wheels of the aircraft fastens to the pavement surface thus almost no work on derubberisation needs to be carried out. Another unexpected advantage is that much less deicing chemical is needed compared to traditional runway pavements. The wearing course is planned for renewal in 2008 and will at that time have had a life of 10 years. During the ten years the pavement has only had one sealing in order to keep the wearing course up to the required standard. For the covering abstract see ITRD E139491.