User blog comment:Kittyfire/Random Topic Blogging!/@comment-3006892-20111004231231/@comment-3006892-20111005143036

Here's what:
 * First of all, the concrete would start absorbing water from your body, so you need to be given water constantly to stay alive
 * The concrete would start leaking toxins into your body
 * Some of your blood vessels would be completely blocked off, making your blood pressure dangerously high.
 * You can't just get chipped away because then all your blocked blood would immediately rush to your heart and all the toxins that were in it will probably kill you.
 * And yes, as the unregistered user guessed, it does make it extremely difficult to breathe.