The difference between concrete and asphalt blades is the hardness of the bond in the segment. To cut effectively, the wear rate of the bond must match the wear rate of the diamonds.
An abrasive material like asphalt needs a very hard bond.
Concrete, which is hard but much less abrasive, needs a soft-bonded segment.
As a basic rule of thumb, the harder the material being cut, the softer the bond, and vice versa.