IMO your ratio is reversed. I'd use 2 gal SH to 1 gallon water. If your using store brand bleach which is 6%SH, then a go stronger on bleach, maybe add another gallon.
Instead of using Dawn, I use a cheap brand of Laundry Detergent, like ALL, or Arm and Hammer, whatever is cheapest and I add a cup, (this is also what I use for house wash.)
For driveway cleaning I rarely use anything before I clean unless it is really dirty like under a tree or something. Once the Driveway is clean then I hit it with the bleach solution and no rinse, just leave it t dry, to really brighten it up, especially when it's sunny out. ALways, pre wet the concrete before you clean though, the wetter it is the better it cleans. Just really opens up the pores of the concrete.
Your ratio of store bleach/SH to water can also depend on whether you ar DS'ing or Xjettin.