In an e-mail from Karl W. B. Schwarz to James Walter
December 06, 2004

In 1989 - there were plans to erect scaffolding and disassemble the WTC towers and rebuild them. Cost projection was around $5.6 billion. One of the architects shows up to work one day and the MIB's were there - had confiscated all of the plans, specs, details, etc for WTC. They even confiscated their office cubicles and had tape on the floor outlining where they went. 
  
Reason - the exterior cast aluminum WTC panels had been directly connected to the steel superstructure of the building, thus causing galvanic corrosion. In short, the "life cycle" of the WTC was not 200 - 300 years, more like 30 years or so. 
  
The exterior skin of the building - in being aluminum and connected directly to the super structure - was making the building weaker every day. 
  
That could explain why there appears to be explosives set only about every 25 floors. Once the failure started, the brittleness of welds, rivets, bolts, etc would fail much easier as the loads became progressively greater on the way down. 
  
That same process would also explain why the concrete was "powderized" over time because electrolytic processes weaken concrete too by "debonding" the Portland that causes concrete to bond in the first place. However, bear in mind that the "concrete floors" were not load bearing reinforced concrete. They were supported by what was a weakening by the day superstructure and cross members. 
  
There was a 1989 meeting and the folks at the architectural firm [Emory Roth, the project architect that took over after the design architects completed the conceptual drawings] that had their office, records, plans and specs seized - were told that the $5.6 billion "take it down, rebuild it" project was cancelled and in about "10-12 years" they would "blow it up and start over". Consider that - and consider that NYC and the US Govt could not stand the global embarrassment of being so stupid or negligent that they did not consider the effects of galvanic corrosion on the superstructure. That is structural design 101 in architectural school and why they want architects to take physics and chemistry for Christ's sake. I did. 
  
I am an architect by the way, quit practicing in 1988.

. . .

Karl W. B. Schwarz 
President, Chief Executive Officer 
Patmos Nanotechnologies, LLC