Hard buildup in cast iron drain pipe

[STurner]

I have started addressing a long-clogged kitchen sink drain that has led me below the floor to the crawlspace and to a cast iron drain pipe that was cracked part way down. I noticed it was filled with a hard brownish material that was impenetrable by auger so I decided to cut off the cracked section, which was about 6-8 inches of pipe. Even below that, right before the elbow, the pipe is filled with a very hard grayish-brown, seemingly metallic substance. I tried drilling the center but even that was difficult. Does anybody have any experience here or know what I am looking at? Thanks, Steve

 

[Terry]

I've seen where people have dumped tile grout down a sink before. Not something that should ever be done.

 

[Sponsor]

 

[Smooky]

Probably cement grout, mortar or some type of epoxy that someone poured down the sink and it set up hard as a rock.