Pulled up some old self adhesive vinyl tiles in a porch today, thin layer of self levelling compound came up with them, leaving a sub floor of really friable concrete screed. Could be crumbled in your fingers.
Tried PVA, helped a little but I conclude that whoever laid the screed didn't use the right mix in the first place.
No point trying to lay anything on top of the screed, so any alternatives to digging it all out & starting again?
More PVA, different mix (I used 5-1)?