But Kuttler says the mass of concrete is 88, and the mass of steel (the *Correct Solid Mass*) is 22. He assumes all the concrete is dustified before hitting the ground, and adjusts r to reach this value. So I don't think your basic criticism is correct.

Kuttler doesn't actually mention the figure of 88 mass units (kg), does he? You got that from me, I assume.

OneWhiteEye said:

Right there, he's implying the mass of concrete - which is all he's trying to crush - should be 110 - 22 = 88 units. But he's already calculated it to be 19.

This is Kuttler's (over)estimate of the total mass of concrete per story leading to the value of 19:

I will assume the floor slab was composed entirely of light weight concrete for the sake of simplicity. In [17] it gives the figure for density of light weight concrete as 1750 kg=m3. Since the floor was about 207 feet by 207 feet and the slab of concrete was four inches thick, this works out to 707,786 kg for the mass of the concrete in the floor.

Total concrete mass is then:

110 x 707,786 = 77,856,460

Varying figures for total tower mass can be found; Kuttler references Greening who states (A) 510,000,000kg and another source saying (B) 450,000,000kg, which is also found

here. Kuttler's own (overly large) estimate of concrete mass in each case is then:

(A) 77,856,460 / 510,000,000 = 15.2%

(B) 77,856,460 / 450,000,000 = 17.3%

For B, the greatest of values, 0.173 x 110 = 19 mass units. The 88 comes from the unaccounted mass (not steel or concrete), the difference total mass (110) between his goal (22 - steel only).

He never detected the disparity. Correct me if I'm wrong, given this clarification.

More relevant is that his estimate of concrete is way too high, and it was clearly not all turned to dust.

And the crushing consisting of comminution to 100 micron size. There

*are* some good critiques of this in the JREF thread. Actual particle cross section distribution probably required far less energy.