I'm sorry she did not make it. I doubt that it was the wet concrete. That is mostly sand and it sets fast. I would wait a month to introduce any chickens to the flock just to make sure that she did not have something that was contagious to the other chickens. I suppose if you were to get chicks you would raise the for a month separate from the adult flock.
If you wanted more information on what caused her death, most state provide low cost or free necropsy. There is more information at this link if you are interested:
https://www.backyardchickens.com/t/40141/link-find-your-state-vet-for-a-necropsy
If you wanted more information on what caused her death, most state provide low cost or free necropsy. There is more information at this link if you are interested:
https://www.backyardchickens.com/t/40141/link-find-your-state-vet-for-a-necropsy