A journal entry about 20 Dec 1864 speaks to your inquiry:

[p. 47] ….. … [W]hen we struck the Central R.R. at Gordon, the desolation was more complete than we had yet seen. There was nothing left of the poor little village but ruins, charred and black as Yankee hearts. The pretty little depot presented only a shapeless pile of bricks capped by a crumpled mass of tin that had once covered the roof. The R.R. track was torn up and the iron twisted into every conceivable shape. Some of it was wrapped round the trunks of trees as if the cruel invaders, not satisfied with doing all the injury they could to their fellowmen, must spend their malice on the innocent trees of the forest, whose only fault was that they grew on Southern soil. Many fine saplings were killed in this way, but the quickest and most effective method of destruction was to lay the iron across piles of burning crossties, and while heated in the flames, it was bent and warped so as to be entirely spoiled. A large force is now at work repairing the road; as the repairs advance a little every day, the place for meeting the train is constantly changing and not always easy to find. …..

Source: Eliza Frances Andrews, The War-Time Journal of a Georgia Girl, 1864-1865. New York: D. Appleton & Co., 1908, 387 pp.

There are a number of contemporary acocunts re the reconstruciton of the railroads.