The observed “partly evaporated” steel members is particularly upsetting to the official theory, since fires involving paper, office materials, even diesel fuel, cannot generate temperatures anywhere near the ~5,180F (~2860C) needed to evaporate steel. (Recall that WTC 7 was not hit by a jet, so there was no jet fuel involved in the fires in this building.) However, thermite-variants, RDX and other commonly-used incendiaries or explosives (i.e., cutter-charges) can readily slice through steel, thus cutting the support columns in a controlled demolition, and reach the required temperatures. This mystery needs to be explored – but is not mentioned in the “official” 9-11 Commission or NIST repor
Thermite is a mixture of iron oxide and aluminum powder. The end products of the thermite reaction are aluminum oxide and
molten iron.
So the thermite reaction generates molten iron directly, and is hot enough to melt and even evaporate steel which it contacts while reacting.
Thermite contains its own supply of oxygen and so the reaction cannot be smothered, even with water. Use of sulfur in conjunction with the thermite, for example in thermate, will accelerate the destructive effect on steel, and sulfidation of structural steel was indeed observed in some of the few recovered members from the WTC rubble, as reported in Appendix C of the FEMA report. (FEMA, 2002; see also, http://www.911research.wtc7.net/wtc/evidence/metallurgy/index.html
http://journalof911studies.com/volume/200609/WhyIndeedDidtheWorldTradeCenterBuildingsCompletelyCollapse.pdf