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Titanium Rebar

For specialized concrete applications
  [vote for,

Reinforced concrete (steel REinforcing BARs are the key) is a fairly popular construction material. However, it has a couple of flaws. One is that if water seeps into the concrete, the steel rusts, and EXPANDS, breaking the concrete. Not very good for a long-term structure!

Another problem is weight; steel is about 3 times as dense as concrete. This limits how tall a reinforced concrete thing can be.

Both problems can be addressed by using titanium instead of steel, as the reinforcing material. In terms of strength, the metal is pretty much the same as steel. But in terms of corrosion.... Shortly after being made, a bar of titanium will quickly and naturally acquire an oxide/nitride coating that protects the metal from deeper corrosion. So if titanium rebars are added to concrete, even if there are cracks that let water soak the metal for a century, it won't be affected. Thus the reinforced concrete structure can be expected to last a long time.

Next, titanium has about half the weight of steel. Therefore a significantly taller structure can be built, than if steel rebars are used.

Vernon, May 10 2015

titanium rebar bridge http://www.newscien...t.html#.VU8p659ArqA
nitinol rebar for earthquake resistant bridge [xaviergisz, May 10 2015]


       Titanium costs about 10× more than steel, which is probably the main reason it isn't used.   

       Corrosion is mainly avoided by sealing and sacrificial anodes. Stainless steel would be another option.
xaviergisz, May 10 2015

       At least Stainless has a similar modulus of elasticity as steel, whereas Titanium has around half. To get the same crack resistance (caused by stress), it seems that twice the cross sectional area of Titanium would be required.
Ling, May 10 2015

       Stainless steel doesn't have anything like the mechanical strength of carbon steel.   

       Standard rebar can be quite effectively protected by hot-dipping in polymer or powder-coating with epoxy.
8th of 7, May 10 2015

       Coefficients of thermal expansion should be matched up, also.
RayfordSteele, May 10 2015

       //steel is about 3 times as dense as concrete. This limits how tall a reinforced concrete thing can be.//   

       Is that really a significant factor? I'm assuming that the rebar adds up to, maybe, 5% of the cross section of the concrete. That means that a beam with rebars will be about 10% heavier than one without.   

       The density of titanium is about twice that of concrete, making a beam with titanium rebars about 5% heavier than one without.   

       So, you're saving 5% of the weight; and that's assuming that titanium has the same modulus as steel. If, as [Ling] said, its modulus is about half, the weights would come out the same.
MaxwellBuchanan, May 10 2015


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