How to remove old black adhesive from 30year old concrete floors? Does all of it have to be removed?
Can porcelain tile be applied directly on adhesive for left on floor from cork and wood floors?

It's best to remove as much as possible of the cutback adhesive. If the area is not too large you could try and rent an electric chipping hammer with the large scrapper blade.

There are thinsets available that can be used over cutback adhesive. Just make sure it says that on the bag.