The normal way that is done, is to stuff it with newspaper to plug it, and then pour a concrete cap.
You may be able to tap it out.
Ok, so I have a toilet drain that has concrete in it. The washroom was retrofitted into an office and I guess they figured that was the best way to close up the drain, so now I need to figure a good way to get it out, any suggestions? The pipe that it's in will be old school cast iron and it's completely covered, the pipe goes straight down and the does a 90, but I can't see that because it's in concrete. Hoping not to have to jack hammer down to get at it.
I once worked a job where the city was clamping down on house where owner converted to several apartments, without permits, and the bathrooms could never be made code-compliant ( in small closets, etc!!!). The city wanted concrete in the toilet drains, and they wanted a LOT of concrete!