Concorde Lover:
It does seem that the last time the Runway was re-surfaced was back in 1985, Although since then it has bound to have had a few repairs or sections replaced due to cracking for example, although i am not 100% sure regarding this.
One of the major differences between asphalt and concrete paving is the fact that asphlat paving is considered to be a "flexible" material, whereas concrete is considered "rigid". This has great implications in the way that the material transfers applied loads to the ground that supports it (the subgrade). Concrete, theorectically, acts as a rigid beam and will provide a more uniform load distrbution to ground below. Asphalt has a tendancy to transfer the load directly down to the ground below at the point where the load is applied. Therefore, in the extreme case of a plane weighting several tons impacting with the runway, you would prefer a material that will distribute the load to prevent the ground below it from settling due to the high loading. Another problem with asphlat is "rutting" and temperature stability. Heavy planes continually following the same routes along the taxiways and runways could cause premature rutts in an asphlat surface (you see this in bus stations too). Also, as temperature increases, asphalt becomes softer and more prone to damage not only from the loading applied by the plane, but also from the wheels grinding into the surface as the plane is turning etc...
