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I'll confess that I have a real issue with iron--it rusts quickly. In fact, the History Channel program Life After People constantly states that, left to its own devices, the iron that makes up a skyscraper's skeleton would have a standing lifespan of 100-150 years before rust weakens the skeleton into pieces.

Long ago, I asked a question regarding the construction of metal weapons without the use of iron at all. In the answers selection, many candidates have been suggested, and they are:

  1. Titanium Alumnide
  2. Nickel Superalloy
  3. Nickel Alumnide
  4. Stellite
  5. Tungsten Carbide
  6. Zirconium Carbide
  7. An alloy of Titanium and Tungsten

What makes this list relevant to the question is that steel or any other kind of alloy had been used to make weapons before their use in construction, so the principle would be identical.

In an alternate, cyber-or-steam-punk New York, Chicago, Dallas or any of the United States' biggest cities, these listed metals and alloys had been considered for construction of mega-towers (a little like this or this or, if you want to go more historical, the artworks of Hugh Ferriss.) Using the science involved, which of the listed metals would be strongest in regards to tension, compression and resistance to corrosion?

Oh, and before anyone asks, this question stresses on quality, not quantity.

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    $\begingroup$ Many of alloys in your list are used for tools: they resist compression and corrosion, but are brittle. A skyscraper do bend a bit by the wind (and potential earthquakes), tungsten frame will crack. Since you want resistance to corrosion and structural stability, consider the marine alloys, e.g.: metalsupermarkets.com/marine-grade-metals $\endgroup$ – Bald Bear Mar 15 '18 at 19:16
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    $\begingroup$ Also, you should consider economics. Corrosion-resistant alloys are expensive. People who build skyscapers do not care what happens to them if they are "left to its own devices". They plan on having their buildings occupied by rent-paying tenants, climate-controlled and maintained. If building ever loses its tenants, it will be dismantled to make space for something else; the only reason to build tall (at least in US) is that land is expensive, i.e. lots of people want to have an office or apartment there. $\endgroup$ – Bald Bear Mar 15 '18 at 19:22
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    $\begingroup$ They reason that we use steel isn't because it's the best for tension (good), compression (good) and corrosion (pretty bad), because aluminum is as good or better at all three of these things. It isn't even just because of cost, because aluminum is almost as good as steel there. Rather it's because we don't make buildings only out of steel, rather we make them out of concrete and steel. And as it happens, steel works incredibly well with concrete because their thermal expansion/contractions rates are so similar, which means that the steel doesn't make fatal cracks in the concrete. $\endgroup$ – RBarryYoung Mar 15 '18 at 19:30
  • $\begingroup$ Here is a large monument that is plated with Titanium, and it remains shiny after 30 years in a polluted city: en.wikipedia.org/wiki/Monument_to_the_Conquerors_of_Space But I cannot find what is the frame made out of. $\endgroup$ – Bald Bear Mar 15 '18 at 19:34
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    $\begingroup$ Whats good for weapons isn't necessarily good for construction, which is why the steel used for weapons is different from the steels used for buildings (there are 100's of different kinds of "steel"). If cost is no object, then I would guess that you probably want some kind of Beta-Titanium alloy tuned to match the thermal expansion of concrete. This could easily have significantly greater strength than steel, yet weigh less than half. Of course it would probably be pretty expensive also. $\endgroup$ – RBarryYoung Mar 15 '18 at 19:58
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If rust is the problem, why not trade iron for stainless steel?

A quick look at coefficients of thermal expansion suggests that you can get stainless steel with a similar coefficient to that of concrete, and because it's so similar to iron, you won't have to change your construction methods much, if at all.

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  • $\begingroup$ Because there is still iron in stainless steel. $\endgroup$ – JohnWDailey Mar 16 '18 at 23:34
  • $\begingroup$ how would you deal with the compounding weight problem? edit: NM I somehow thought he was building to space lol $\endgroup$ – Belqinor Mar 18 '18 at 8:31
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Researchers at MIT have used graphene to develop a lightweight material that’s 10 times stronger than steel that could potentially be used to manufacture vehicles and devices, as well as in building construction.

A team of researchers in MIT’s Department of Civil and Environmental Engineering (CEE) designed the 3D material—one of the most lightweight and strongest ever developed—by compressing and fusing flakes of graphene, a two-dimensional form of carbon. The result is a sponge-like configuration with a density of just 5% that is incredibly strong, they said.

Graphene, in 2D form, is believed to be one of the strongest of known materials, but its strength in the 2D world has been difficult to translate in a 3D material. Graphene has exceptional strength, but because of its extraordinary thinness, it is not very useful for making 3D bulk materials that could be used in vehicles, buildings, or devices without first translating graphene into three-dimensional structures.

The geometrical configuration of the is the dominant factor in their characteristics and the success in using graphene to design them.

Researchers developed the material by compressing small flakes of graphene using a combination of heat and pressure. This process produced a strong, stable structure with shapes that resembled some corals and microscopic creatures called diatoms

~credit: "designnews.com" and "MIT.com/CEE" respectively

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  • $\begingroup$ Also, 5% density carbon is SUPER easy to get in bulk. Making it a choice material. $\endgroup$ – Belqinor Mar 16 '18 at 10:22
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Why metals at all? Concrete and composite rebar (carbon fiber reinforced plastic, glass FRP, aramid FRP) construction is now used in structures such as bridges precisely because they do not rust, and are light. Such technology could be applied to concrete skyscrapers.

The same technology applies to truss structures. There is a clear path today towards replacing structural steel with composites.

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    $\begingroup$ Skyscrapers need the ability to sway in high winds. Concrete is poor at that. $\endgroup$ – RonJohn Mar 17 '18 at 5:50
  • $\begingroup$ @RonJohn And composites are even better than metals at swaying (cyclic stresses) because they do not fatigue. That's a huge reason why they're building airplanes out of it. $\endgroup$ – user71659 Mar 17 '18 at 6:07
  • $\begingroup$ Your answer is about concrete using composite rebar, not about buildings made of composites. And no one wants to be in a building that sways as much as a Boeing 787 wing bends. $\endgroup$ – RonJohn Mar 17 '18 at 6:19
  • $\begingroup$ @RonJohn Your comment about concrete is factually wrong. Multiple skyscrapers, up to 100 stories, are concrete. Please don't be mean-spirited and pedantic. Of course a skyscraper is not going to be built the same way as an airplane wing. Composites are a clear replacement for structural steel and other metals. Are you doubting that? $\endgroup$ – user71659 Mar 17 '18 at 16:05
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    $\begingroup$ @RonJohn: I think you have it backwards. There's no fundamental need for a structure to sway in high winds. Rather, (and simplistically) buildings using steel-framed construction sway because the steel is flexible, so the building must be designed to handle that. At the opposite end of the scale, there are concrete dams up to 1000 ft/300 m tall, and I doubt they sway much. $\endgroup$ – jamesqf Mar 18 '18 at 1:32

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