Quote:
Originally Posted by PHI215skyline
Fireproofing might be referring to the flame retardant spray they use on the interiors of the building, such as the steel framework.
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in 1885 they used pores terracotta tiles to sheath the steel frame against fire(invented by the Wilson Brothers of Philadelphia)
by 1970 there were using asbestos and now today a type of concrete
in the 1850s some structural iron buildings of around 5 stories built in NY and Paris had fires and suffered catastrophic collapse. This came as a surprise to the engineers of the day. The iron, like the steel in the World Trade Center, when exposed to 1500+ deg F for 45 min or so did not melt but did lose its strength.