I drilling somewhat deep holes (inch and a half) into concrete and I'm hitting something hard in two out of my four holes. I'm fairly sure it's not metal I'm hitting and I'm wondering how to proceed. It's a new building (finished half a year ago - in October 2018) and it is in Sweden, so I'm sure modern building standards have been followed.
I'm using a proper rotary hammer and a proper concrete drill for the job and as far as I can tell the tip is not getting dull or anything. Could it be a rock or something? Or is modern concrete fairly uniform? Any suggestions on how to proceed and get past this obstruction?