Yes, Rusty makes a very valid point on safety. I used to set my chimney directly on my driveway a few times with no problems. You can see the slight orange discoloration in the concrete. But I always set my starter cube on a small paver.
The last time I did it, I couldn't find my small paver so I just placed my starter cube on the drive ( Wrong ) I was getting ready to bend over and pick it up, and I heard a pop like a firecracker and a piece of concrete shrapnel blew by my face.
Concrete hold moisture for a long time, and if you quickly hit it with a High heat source it causes thermal shock.
I was lucky I didn't bend over a few seconds earlier cause these are pics from the crater left behind.