I don't have a grinder . I tried hammer route and it seems that the type of nail they use is hard to be broken. I have been hammering in many direction for 30 minutes to a nail and it has not broken off yet. The concrete around it chips off :furious:Smacking them with a hammer will usually break them off and you can hammer down the sharp edge at that point.
Don't bother pulling them out. You will do more harm than good.
If you don't go the hammer route, just an angle grinder with a cut off wheel will work.
+1Assuming you are going to insulate again, leave them. They won't hurt anything to build a wall over them and insulate.
+1 to that, one of the most useful tools I own, and they're fairly cheapFix'n it said:go buy an angle grinder ! they are not expensive. easy to use. have a ton of uses. and will save you a ton of effort and time.
get several(pack of 10) cut off wheels, they are the skinny ones. and a few grinding wheels, the thicker ones.
you can thank me later.