I have two issues to deal with.
1. I have a section of floor that was cut out and filled with white stone where the hot tub was, about 8x10 area. This stone is about 4 inches deep, can I mix in some concrete mix to solidify the stone and then apply a layer of skim coat over that to level the space??????
2. I removed some indoor outdoor carpet but the glue stayed on the floor, it's rock hard and appears to level out the floor nicely, can I tile over it????
1. drill into the 4 sides of the cutout and install rebar. This will joint the old to the new. The concrete should be about the same thickness as the existing floor. Fill with concrete, a trowel flush with the old. If still not even after it dries, some leveling compound will bring it up. But use a membrane in this are, as there will likely be some cracking over time.
Do as Bill says. Get those stone out of there, prepare the base and have it poured. It'll take exactly 1 yard of cement.
You'll have to cut the adhesive away and get down to bare concrete. Try a tool called a "wallpaper scraper". It has a handle with a 4" razor blade on an angle, should work pretty good. You should be able to go over the concrete after you do the above. If you have the time, it would be a good idea to do several "test-bonds" and allow to set for a week or 2 to be sure.
TILE GUY - retired- TROY, MI - Method & Product suitability consulting.