Help - How do I seal this mess

[myhooose]

I have a complicated joint in the floor where an old fireplace used to be which dampness is penetrating. If you can bear with me I'll explain.

The floor was suspended timber but is now concrete with a black bitumen epoxy type coating. When this coating was laid the fireplace must have still been in place. Since then the fireplace has been removed. The area lined with a dpm and filled with concrete 15mm lower than the floor level and a leveling screed and epoxy coating applied to seal. Around the perimeter of the fireplace is a slate or similar material wall 20 mm thick between the old and new concrete. This is just a few mm lower than the floor level in places.

The area is damp and the epoxy covering over the fireplace has lifted and failed with salts present underneath.

Does anybody have any idea how to sort this out. I've removed half the failed epoxy coating and leveling screed

Thanks.

 

[myhooose]

I've found a solution, A local mastic asphalt specialist is coming to have a look. They can also re level the floor in my hallway too.