Levelling deep spots in concrete floor
At 3” I would mix up a batch with turkey grit much larger than sand but smaller than pea gravel. I have used this mix to level garages that had a similar slope to the door when making them a living space.
The existing floor needs to be clean and I would do a heavy etch of muriatic acid and water. After rinsing I would put down an adhesion promoter then start your pour.  I have done this by hand mixer Several times but one case I did get what I needed on a short load , much easier, I did have to wait a few extra days but it was worth it!  only a yard and a half but hand mixing the start is almost set by the time you finish So it takes 3 or that’s how we did it 1 person on the mixer the other two raking &amp; floating. But we did this close to a dozen times to add living space.