I recently got my foundation repaired and am left with a very cracked and uneven concrete floor next to the wall. Along the very edge any leveling compound would be at least an inch deep. All I plan to do in the room is put down some epoxy floor paint and turn it into a workshop. So basically I don't need it to be picture perfect, and self leveling compound is very expensive, so I was wondering of mortar would work well enough in this situation. My primary concern is whether or not it would adhere well enough and whether or not such a large slab of the stuff would be prone to cracking. Any advice would be greatly appreciated.
Mortar will most likely crumble.
To ensure good adhesion, you could cover the existing floor with PVA before mixing up some granite chips with a little sand and plenty of cement. Leave it a little low, and don't bother where you need only a thin covering, then you can cover the whole floor with a thin self-levelling screed to give you a smooth finish all over.
Leveling using mortar is not acceptable in so many ways, but most important one is that it would crack. Even if it doesn't crack (and it will) you will have a problem because it is workshop: every time you drop a hammer or something you will damage the floor. Self-leveling compound is the best solution, by far but if that is not the option than I suggest one of two options: first would be not to touch anything; yeah it is damaged and uneven but since it is a workshop maybe you shouldn't care about it. Another solution is to make a cement screed which then would be covered with some flooring. This solution is only possible if there are no "level obstruction”; meaning all the doors can open there aren't any small steps between rooms which would be a problem for you etc.Also instead of screed you can pour thin concrete slab, but concrete should be made out of fine (small pieces) gravel.