Black adhesive on concrete floor

[Carts69]

Hi, I have just removed old tiles from kitchen floor with a view to laying ceramic tiles,the floor is now thinly coated in a black adhesive that is not wanting to be removed easily, despite throwing everything at it!
I read that a slurry coat is the best way to go, my question is....can I slurry coat straight over the black as is, or does most of it need removing prior to slurry?

 

[ree]

A posted pic would help?

The black stuff could be either a bitumen adhesive that was used to set the old (ceramic?) tiles - or a DPM substitute to cover the slab surface against any damp.

Is this stuff a hard brittle shell?

Does it have ridges from a notched trowel?

 

[Carts69]

Yes, it's hard And brittle & chips of little by little, also yes there are thin ridges running through it, so it has been troweled on! Any ideas ree?

 

[ree]

You can continue to chip it away to leave a clean background - thats a best practice approach.

Or, you can knock off any high spots and then prime, & pour a thin layer of SLC. But first call the SLC Mfr's for further advice ref the bitumen.

 

[dazlight]

Grind it off. If solid you can put Ardex NA screed over it

 

[simonpolly]

Also for future reference the tiles you removed probably contained asbestos,Marley tiles i think they are called it was common practise in the 1970s to lay them on a coat of bitumen.