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portland cement has a density of 1.44 (that is, m^3 of portland cements weighs 1.44 times that of a m^3 of water).  Concrete can go as high as 3 with very dense aggregate.  Are we talking about trainloads of cement here, because any load will be subject to the axle loading of the rails which sets an upper bound on the train linear density.

Or are we talking about the tube itself?  I was considering the tube to be made of steel alone, but now you mention it, a ferrocement design would be much lighter (steel has a density of about 8).  There are many ferrocement boats out there and ferrocement is lighter than concrete.

by njh on Tue Dec 22nd, 2009 at 06:27:27 PM EST
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