Hi Miers
Chickens will be fine on concrete, you can hang up greens (cabbage, nettles etc) for them to peck at for amusement and vitamins. Just make sure you use a good layers feed.
I use bark chips (from a garden centre) as a base covering from my breeding stock although old bark which has rotted may casue a problem with fungal spores. Some people will use 2cm gravel as this can be hosed out to remove all the poo.
Loz
