Burning fuel can't melt concrete and rebar!!
Actually, yes, it can.
The Yale Architecture School building is an all-concrete, "brutalist" style building designed by one-time Dean of the school, Paul Rudolph. The entire structure is reinforced concrete. Back in the 1960s there was a huge fire in one of the studios. I knew a guy who had graduated from college a year before me who was a student there at the time, and he said it was common knowledge that the fire was started by a disgruntled student.
t was near the end of the academic year and all the students were heavily into their final projects, so all the studios had lots of paper (plans) and cardboard (for models) in them. The fuel load was quite large, and the fire developed enough heat to soften the reinforcing bars in one or two of the top-most stories and the roof.
In this photo, I think everything to the right of the tower just right of center is a later addition: