In 1948, Herbert Levine invented an inexpensive, compact, lightweight, spray-on structural steel thermal insulation comprised of asbestos and rock wool.
In 1971, when the WTC towers were being constructed, the city of New York banned the use of asbestos. But the builders could not go back to the method of skyscraper construction used for The Empire State building and other, older skyscrapers because the steel frames used in them were insulated by a couple feet of concrete. Doing this would have added too much weight to the top floors for the lower 64 to support.
The Port Authority wasn't about to tear down the half-completed structures so the builders rigged a non-asbestos "substitute". Back in the 70's, Mr Levine said if a fire ever breaks out above the 64th floor, the tower(s) would collapse. He was right...
-information from Durk Pearson, "Reflections" - Feb 2002 "Liberty" magazine
In 1971, when the WTC towers were being constructed, the city of New York banned the use of asbestos. But the builders could not go back to the method of skyscraper construction used for The Empire State building and other, older skyscrapers because the steel frames used in them were insulated by a couple feet of concrete. Doing this would have added too much weight to the top floors for the lower 64 to support.
The Port Authority wasn't about to tear down the half-completed structures so the builders rigged a non-asbestos "substitute". Back in the 70's, Mr Levine said if a fire ever breaks out above the 64th floor, the tower(s) would collapse. He was right...
-information from Durk Pearson, "Reflections" - Feb 2002 "Liberty" magazine
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