Tarmac is actually a short way of saying Tar + Macadam or sort of an asphalt. Tarmac has been "generalized" to mean any airport paving like Kleenex is used for tissues.
Just about all high temp locations, and others, use concrete, not "Tarmac". I have no clue where on Reagan the incident took place but it might have been at a part of the terminal area that was actually Tarmac and not concrete since Reagan National is so old. They also sometimes cover the underlying concrete with asphalt since it is easier to maintain and repair.
The Commuter slots were likely paved to support lighter weight aircraft and as commuters (both airplanes and people) grew in size, they got too heavy for the paving on a really hot day.
Just Some Consultant
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Last edited by X3 Skier; 07-09-2012 at 11:57 AM.