If it's just portland cement dust that got blown by the wind onto the asphalt, I'd just hose it off with a garden hose or maybe blow it off with a leaf blower if you have one.
Or, just get it wet, agitate with a push broom, and vaccuum up the water with a wet/dry vaccuum cleaner.
Fresh concrete is highly alkaline, and so if there's any concrete staining left, you should be able to remove it with a mild acidic cleaner. CLR, Limeaway or any phosphoric acid based bathroom or toilet bowl cleaner in the hardware store should dissolve fresh concrete. Certainly muriatic acid would dissolve the stuff, but that's like using a sledge hammer to break an egg.
You don't need to know the rest:
"Asphalt" is what's left over after distilling crude oil. After you boil off the gasses like ethane, propane and butane, and the fuels like gasoline, kerosene and fuel oil, and the lubricating oils, what's left in the pot is asphalt. They mix asphalt with stones (and probably other stuff to stabilize the asphalt so it doesn't soften as much when it gets warm) to make asphalt for road construction. In other countries, asphalt is called "bitumen".
http://www.elmhurst.edu/~chm/onlcourse/chm110/outlines/distill.html
"Tar" is the residue left from the distillation of coal. When they used coal to supply gas for "coal lamps" in the city, tar was a plentiful and cheap byproduct. Now that we use crude oil to get gasoline for our cars, asphalt is a plentiful and expensive by product. Tar is also called "pitch".
