concrete-head

noun2

1. •
   (informal, offensive) A stupid person; sometimes one who is being stubborn to the point of stupidity.

   • As far as I can determine, I am a bleeding heart liberal. Personally I think that's way preferable over a concrete-head conservative, if given a choice between the two. — 2004
2. •
   (slang, disapproving) A person who is stuck in their ways; one who is unwilling to try new ideas.