I always wonder why people say minimalism doesn't mix with concrete.
The whole point of minimalism is that if you do it with correct form there is no sharp impact as with heel-striking. So if you run correctly in minimalist shoes on concrete, it will be a lot better than heel-striking...on any surface!
Now if you want to say avoid concrete no matter whether you are minimalist or not, then that's a different matter, but concrete isn't going to increase impact more for a minimalist than someone who overstrides.
The only reason that avoiding concrete with minimalist shoes vs. the amount of time you normally do with regular trainers would be legitimate, would be because minimalist shoes wear down quicker (usually) so therefore running on softer surfaces would prolong the life of the shoes.
If you do minimalism with correct form, which takes time to perfect, the only injury risk you will face is the fact that your muscles are working a little bit differently, which is a concern. But if you improve your form and get past the initial stages (possibly soreness), you'll be glad you switched.