Not long after the Oakland Hills fire in the early 90's I was talking with a homeowner. I ignorantly said that at least he can still rebuild on the same foundation. He said that at about 2,000°F the rebar in the foundation gets hot enough to expand, leaving voids in the foundation when it cools, and at over 2,500°F all the water gets cooked out of the foundation, leaving you with a pile of concrete dust that looks like a foundation. In either case the foundation has to be replaced. The extreme temperatures created from the burning eucalyptus trees were supposedly responsible for those temperatures.
My question is twofold:
- Are the temperatures cited more or less correct?
- Are these temperatures encountered in a non-wildfire environment where the only fuel is the structure's flammable materials?
It seems like rebar would get hot enough to expand well below 2,000°F.