Hope this thread isn't too old. I'll add that you'd definitely need to treat it with some coating or it'll stain. Concrete is very absorbent. Go to any store with a bare concrete floor and pour some water on it. Wait a bit then mop it up. You'll see it's less wet than you'd think it should be and there will be a dark spot from the water soaking in. It'll work on you driveway too, but is more impressive on a finely finished interior floor.
The smoothness of a floor intended to be bare concrete is achieved when it's poured. There's really no way to make cured concrete super smooth. Most exterior concrete is intentionally roughened (broom finish) to make it less slick.
Bridge decks are often sealed with Methacrylate (some specialized epoxy). It's poured on and squeegeed around. It's incredibly slick though, so has to have a sand spread on it before it cures. It seems like the more durable and pretty coatings are, the slicker they are.