I am in the process of replacing my old porcelain/steel tub. I've replaced tubs in my previous houses and never had a problem like this. When I removed the old tub, I was somewhat surprised to see the entire drain assembly encased in (what I thought was) light weight mortar. The house is built on a slab and it appears that the contractor framed in an area for the bathtub drain to sit below the tub, hooked up the plumbing and then filled the area with mortar to ensure that the pipes would not move. I was going to replace the drain anyway since the offset from the back wall of the enclosure to the new drain in the replacement tub differed by 2 inches. No problem, I thought; just chisel out the old mortar until I had enough room to work, pull the old drain and put in a new drain/overflow assembly. To my surprise, the mortar was just a thin layer, no more than 1/2" thick. Once I got through this layer, I was horrified to see that they entire cavity surrounding the tub drain was filled what appeared to be pitch or asphalt (minus the aggregate)! I can't chisel it; the chisel just sinks in after one hit. I can't cut or saw it because it heats up and clogs my saw blades and then flows back into place. Has anyone ever heard of this and more importantly, how the #$%@ do I get this stuff out of here? Any suggestions will earn you a well deserved "ATTABOY".

Thank you

Maybe soften it with a heat gun and scoop it out ?