I...don’t think they do... If I had to take a guess I’d say that their pee is mixed with their poo. Also fun fact. The little ant hills you see everywhere are made from ant crap. So every time you’ve stepped on one of those, you are essentially stepping in poop.

I don't think so. I've often seen ants carrying little grains of dirt out of the anthill and setting them down in the pile. It makes sense to me that they just excavate by digging out dirt with their jaws, and then set it down by the entrance making a hill.

I think they mix it together to make the dirt easier to mold. Like adding cornstarch to clay. Flour to dough.