How to remove black gunge (bitumen?) from concrete?

[MikeMinh]

We removed two layers of old vinyl, and two more layers of possibly lino tiles from a solid floor in a kitchen.

Left are sizeable patches of a black gunge, might be a glue, might be bitumen, but I can't be sure. It's slightly sticky, but not everywhere.
Area is approx 14 m2 in a 1930s house, concrete floor. I don't think this was a DPM. Floor is otherwise perfectly dry.

How do I remove it before we put a levelling compound on top? Advice from a well respected local tiling shop is:

• *Remove 'bitumen';
  *prime with Mapei Eco Prim grip,
  *use Mapei Ultraplan Renovation screed to level the subfloor
  *eventually lay sheet vinyl on top (which I bought before I knew what was going to hit me).

The shop in question was helpful up to a point, but they wouldn't take the job on, unless they do the whole job including laying and selling floor materials.

I'd appreciate some advice.

Many thanks

Mike

 

[kbdiy]

Heat gun to soften and scraper to lift it would be my first try. It might even scrape off without heat which might be less messy.