I have an old photocopy (with some blank spots in it, including part of a section on bridges) of Charles Totten's 1880 "Strategos: A Series of American games of War Based upon Military Principles..."
In Volume II, pg 23, Table G ("Time required for various purposes) includes:
98. Destroying a pile bridge........... 2 to 6 hours
99. Burning a wooden bridge (esch 50'), Case 5 Table II................ 30 to sixty minutes
100. Extinguishing same, if possible (after 20 minutes, 10:1 against) 15 min- 1 hour
101. (Repairing ?- illegible) same (practicable for passage) ...... one-half to 24 hours
102. " completely .................................... 1 to 5 days
103. (Illegible) work under fire ................................... half to twice longer
104. " " under heavy fire .............................................. Case 15 Table I

A 25' to 30' Railroad Bridge, material at hand, can be built in about 6 hours; longer or very high bridges require much more time.

He also has "One half an hour burning is generally sufficient to render a bridge, without repairing, impassable to an enemy" - CULLUM

In de Brack's Light Cavalry outposts, he says "A charge of 40 lbs covered with sand bags, or 60 pounds uncovered, will make a breach 6 ft wide through a stockade of timbers 10 inches thick...Any single line of stockade, when the timbers do not exceed 14 inches thicjness, may be breached by a charge of 100 pounds of powder, uncovered, placed on the ground and in contact with the timbers... a double stockade may be breached by 200 lbs of powder... A 14 inch wall, however well-built, can be breached by charges of 60 lbs, weighted with sand bags, the charges not being mor than 5 or 6 feet apart... When a town gate has to be breached, it would be unsafe to depend on a smaller charge than 200 lbs of powder covered with sand bags.

- Ned