I don't think concrete sand is as clean as playground sand but they poop on it anyway. There isn't any extra stuff in it, is there? What we use is the big bags from Lowes that are outside, HUGE canvas bags that they put in my truck with a forklift.
I read that for aquariums to not use concrete sand because it may have added chemicals to help in making the mortar. But the bags sold at the larger building stores should have a list of the ingredients of its contents.
We just put a trailer load of concrete sand in our run and coop. We bought the sand at the local gravel pit. No additives - just sand. So far, so good. It has some larger bits for grit, and some smaller bits. The chicks love to scratch and dust bathe in it. I wanted "river sand" but all they had has concrete sand, which, I gather is the same thing. I am a fan so far.