[skybrian]

Modern concrete has steel rebar, which is very useful, but eventually corrodes. Stainless steel rebar could be used if longevity mattered, but usually it doesn’t because the building will likely become functionally obsolete and need replacing before then.

[benj111]

Define functionally obsolete.

Ultimately most tall structures as a reinforced concrete skeleton with glass hung on the sides.

It seems to me that as you're going to replace it with another basically identical concrete skeleton it makes sense to have that skeleton last as long as possible. And then refit that skeleton.

[smalltorch]

It only corrodes if it's not completely encased in concrete. The concrete stops the reaction. And, if one portion of the rebar is not encased it will eventually corrode through overtime.

[adolph]

This is something I wasn't aware of that is fascinating. The ph balance of the rebar's environment determines the progression of oxidation. There was a guy in the 1920's who observed this and had the idea to put cement in paint; it was so successful he renamed the company to cement spelled backwards.

  Inside the concrete, Ca(OH)₂, which is generated by the hydration of cement, 
  creates a strongly alkaline environment, with a pH value of more than 12.7. 
  In this environment, a passivation film forms on the surface of the rebar to 
  prevent corrosion. However, the pH of the concrete decreases as micro-cracks 
  develops and chloride from the outside infiltrates the rebar. Eventually, as 
  the environment inside the concrete becomes neutralized, the corrosion of the 
  rebar accelerates, which reduces the overall durability and stability of the 
  reinforced concrete structure.

https://www.sciencedirect.com/science/article/pii/S095006182...

  A sighting of preserved steel reinforcing bars sticking out of old concrete 
  rubble piqued the curiosity of our company founder, Albert C. Bean, Sr. After 
  investigating this finding, his company, Armor Oil & Chemical Company, began 
  producing a patented cement-filled coating formulation that, in its updated 
  form, still protects structures from corrosion today.

https://tnemec.com/about/

[masklinn]

> Stainless steel rebar could be used

There are also coated and non-metallic rebars.

[terribleperson]

Coated rebar could be good, but the coating can be damaged anywhere from manufacture to installation.

[masklinn]

Yup, every alternative rebar has drawbacks which causes increased costs or different failure modes which is why they tend to be used in specialised applications where they are necessary.

[warumdarum]

You could wouldnt even need that. https://de.wikipedia.org/wiki/Opferanode

[eru]

Yes, but you have to replace the sacrificial anode every so often.

https://en.wikipedia.org/wiki/Galvanic_anode

[Barbing]

Like the plate of food on the grass for the bees at the barbecue

[beeforpork]

Wasps, not bees.

(Sorry, I'm a bit of a nerd. But I am sure you can cope with that.)

[kps]

Does pork factor into this? (Serious question for an expert, not a joke.)

[Barbing]

You did ask the bee for pork

[Barbing]

Retract my bee slander!!

[eru]

More for the wasps, I guess?

[jaapz]

Wait, does this actually work?

[Barbing]

Just wish I could claim credit. Decoy plate is essential.

And since nobody complained it sounds wasteful, I suppose it should be able to be just scraps.

May your next camping trip or picnic be wasp free!

[eru]

It sure attracts the wasps. Whether you have less of them on your real food compared to the counterfactual, I don't know.