I may be mistaken but I think that the floors in Durango were cinder and dirt untill the 60's. I will take a look in some of the books that I have, but I am almost certin of if.
I do know,however, that the ATSF roundhouse in Emporia KS was concrete. I know this because I found it one day while walking in the rail yard. The building is no loger there, but the floor and rails are. I was just walking around one day and came across a set of rails that were embeded in concrete and brick. I walked to where the end of the concrete was and began to follow it around. I began counting stalls and came up with 35. That is one big roundhouse for the middle of no where kansas.
John V