Laying slate tiles on to bitumen

We have black stuff on our concrete floor (may be cut back) its not sticky its smooth what primer could i put on top before laying the slate or what should i do

We would recommend that if you are just laying slate tiles on the adhesive then to prime with 1:1 adhesive & Acrylic Bonding slurry. If you need to use a levelling compound then you must use an epoxy primer. The reason to do this is the adhesive is more forgiving on bitumen than levellers. We would also advise you use a flexible adhesive to lay your slate tiles on to the substrate.