It's concrete. Concrete is either cement and ballast, or cement, sand and gravel.
Ballast is just a mix of sand and gravel. So the end result is the same. There are different strengths and mixes of concrete.
Your post doesn't help anyone to understand your problem.
If you're filling a trench with concrete, why does it need to match any other concrete.
Backfilling refers to refilling a trench with the spoil that came out of it.
Gio,
so you have made a trench in your (say) drive.
And you want to fill this trench so that its surface matches the concrete that is already there.
Sorry to say that that is near impossible.
For my two penny's worth,
Using Balast will fill the trench perfectly and make for a good job.
But Balast will make a 'flat concrete' that is unlikely to match the pebble finish that you currently have.
Without experimenting (and likely still failing) buying you own pebbles and sand will make for another different surface finish and still not match what you already have.
SFK